Possible the most regrettable thing I've done in the last 5 years photography-wise has been selling my lovely D200 and the small selection of lenses I'd acquired for it - along with the 35mm f/2 Nikkor prime it was pretty much the perfect walking-around-low-light camera. Its only sin was being bulky, and when you're travelling a lot you have to be determined to take such a lump of camera with you. After too many camera-less trips (or with only the Canon G9 compact I have for these occasions) I decided I wasn't using the D200 enough and sold it - and since then have been either pining for my lost love or plotting its replacement. Last December I made a somewhat experimental purchase of a Panasonic G1 (with the 14-45mm kit lens), which I'm still pretty happy with - Micro Four-Thirds has potential - but I'd be much happier if some fast prime lenses got delivered for the format. I'm not sure how long I'll be sticking with it - this still remains to be seen.
It should be clear from this that I've done quite a bit of thinking about what's "the right camera" for my areas of interest (trains, cycle races, or just walking around looking for stuff). At the same time I've noticed a lot of assumptions that "if you want to take good or creative pictures, you need an SLR". I'm just one person, but hey, I figured I'd put my thoughts down on the subject anyway..
Firstly - you're likely to miss out on some of the best pictures you'll ever take, simply because you didn't have a camera with you when the opportunity arose. By this rule the best camera is whatever you have to hand! If you miss out on a great shot because the only camera you own is a giant SLR which can't slip into your coat pocket, you lose. If you're either lazy or simply opportunistic rather than going out specifically to look for shots, you'd be better off with a decent quality compact. Sure, you can own a big camera too, just don't assume that you'll always have it with you.
Secondly, you don't need the latest whizzbang SLR to take creative pictures. While if you don't have a camera at all the current crop of budget SLRs are a great introduction to this type of photography, don't dismiss the little point-and-shoot compact you might have already. There's more to an image than the camera which created it, and in some cases it can force you to think differently if, say, you only have a small-sensor compact to work with. This is good for creativity - don't confuse "creative" with "technically perfect". The tyranny of the Internet leads to hilarious things in this area - such as when a fantasic, but less than technically perfect, image by Henri Cartier-Bresson was posted to Flickr for comment. One of my own favourite photos is from a tiny point-and-shoot - it isn't technically great, but I like it far better than many, many of the shots I've taken with a thousand quids' worth of kit because I think it perfectly captures the atmosphere of a damp London evening.
I'd actually say, based on my (limited, aye) experience, that if you want to get serious about taking pictures you could do worse than to make do with what you might already have for a while. Take lots of pictures and learn to work within the limitations of your equipment. When you find yourself looking at a shot and thinking that it would have been a better picture had your camera had a particular feature, make a note of it. After a while you'll know your own style and you'll have a better wishlist for when you go camera shopping.
You'll also discover that when you get into the SLR world, the right lens is far more important than the right body. Most kit lenses that are supplied with, say the Nikon D40 or the low-end Canons are designed both down to a price and for the broadest range of applications - they're usually mid-range zooms with so-so maximum apertures (say, f/3.5-5.6) and will do a workmanlike job. Like the lenses in compact cameras, though, when the going gets tough you may find them wanting, and you'll be disappointed that the results you're getting out of a DSLR aren't much better than your zoom compact under low-light conditions or when you're trying to control the depth of field to bring out a single subject.
In the old days, every 35mm SLR owner would inevitably start with one lens - a wide-aperture (say, f/1.8 or f/1.4) 50mm prime. For a 35mm frame, a 50mm lens has about the perfect balance - its perspective closely matches what a human sees, it has a decent field of view, and they're optically very simple requiring few design compromises or tricks to produce an excellent, sharp image. The wide aperture meant far better control of depth of field, a brighter image in the viewfinder, and the most light for autofocus systems to work with. Then, zoom lenses increased in quality and availability, and marketers started insisting that a mid-range zoom would be the obvious kit lens to sell to first-time camera buyers. This is a hard argument to resist, as for salesmen in shops it's far easier to sell "multiple lenses in one!" than it is to blah on about depth of field and optical aberrations.
Nowadays manufacturers attempt to compensate for such slow lenses with things like optical image stabilisation to correct for camera shake, but the fact remains that a good prime lens will get you the shot with a shutter speed at least twice as fast as a consumer zoom. f/1.8 vs f/3.5 is about 1.75 stops faster, or the difference between a shutter speed of 1/30 and a perfectly hand-holdable 1/100. Don't forget that image stabilisation won't help with moving subjects, either - it'll only stabilise the background!
So if a 50mm lens is so great, why did I talk about how great the 35mm f/2 lens was on my D200 at the beginning of this piece? Well, because on today's small-sensor digital SLRs (essentially, all the available models until you start paying enough for a body that you should really know how large its sensor is before buying it), a 35mm lens is actually closer to the "50mm equivalent" field of view, while a 50mm lens has become a short telephoto.
The problem here is that at least in the Nikon world, the low-end SLR bodies can't do autofocus with a lot of lenses which use the older technology of focusing via a motor built into the camera body rather than building the motor into the lens. This means that virtually all prime lenses you could put on a D40 or a D60 would have to be focused manually - which isn't as easy as it could be as they lack the sort of focusing screens which were essential in the days of film. So if you want the convenience of autofocus, you're stuck with zooms. I'm guessing that third party manufacturers may make internally-motored primes, but I'd also guess that they'd be pretty pricey.
Or, at least, you used to be stuck. Nikon recently surprised everyone by introducing the AF-S DX NIKKOR 35mm f/1.8G. This mouthful of letters tells you that this is a most interesting lens - it's a 35mm prime lens, with a nice wide f/1.8 aperture, which is specially designed for DX (small sensor) SLR cameras and has the AF motor built into the lens so will work with the D40 et al (AF-S). Best of all, it's cheap. Hot dog! With one smart lens release the D40 et al are suddenly "serious" contenders for people who worry about being able to craft the image they want rather than what their equipment will allow but don't want to spend thousands of pounds on cameras first.
I guess that what this means is that right now, if I wanted to take creative photos with lots of control over the image and didn't own a camera at all or had decided that I wanted to step up to a DSLR, I'd seriously consider getting one of the inexpensive non-AF-motor-fitted Nikons (a D40 or, better, a D60, or even better, a D5000, but then it's getting pricey), putting the kit lens into a drawer or just keeping it for wide-angle use, and getting the AF-S 35mm (about 280 francs in Switzerland, 200 quid or less in the UK.. hm, cheaper to buy it in Switzerland, which is unusual). After all, who needs a short zoom anyway? You can just move the camera back and forth.