Since I've come into a bit of money, I decided to buy myself an early christmas present: a Canon 20D. It is my first SLR camera and here's my 20 øre worth of opinion about it:
The 20D looks quite bulky when you take it out the first time, especially if you are used to compact or prosumer digital cameras (like my previous one, the Minolta A1). It is also on the heavy side. If you are thinking of buying a camera like this it is something to think about; do you want to carry this weight around?
On the up-side here, the construction is very sturdy indeed and looks like it will survive the odd raindrop as well (no I haven't tried this). In any case it is obvious the camera won't break apart after using it for a while, which unfortunately can be the case with some of the compact models.
Initially I got it with the 18-55mm kit lens. While this lens is good value for money (It's only about €75 or so) it isn't all that great in general. It feels cheap and plastic-y and several reviewers have noted problems with purple fringing (chromatic abberations) as well as other image artifacts. Although this lens might do the job reasonably well, I must admit having it felt like putting discount tires on a porsche 911 (no I haven't tried this either).
So I ended up trading it in for the 17-85mm Image Stabilized (IS) lens. Now this lens is a joy to use. The zoom action is smooth and focusing is really fast and virtually silent. It does take some getting used to though, on account of the image stabilization. It doesn't give any feedback on whether the shutterspeed selected will produce good quality images if IS is used. With some practise this will likely become second nature however.
On to the camera itself. The first thing you'll notice and will continue to impress you is the sheer speed of it. You can turn it on, press the shutter halfway to get focus and shoot a picture in less then a second. Most of that time is spent moving you hand from the power button to its proper position under the lens. This is a minor gripe though: the power button is quite hard to operate. It is stiff and hard to reach. This is probably a result of trying to ensure the camera doesn't turn on by mistake, but I can help feeling it could have been better. Note however that you can use the camera in stand-by mode too. Basically you can set the camera up to turn itself off after x minutes and then turn on again by pressing the shutter button. Again, fast as lightning.
My previous camera was setup up to always run in continuous shooting mode, so holding down the shutter would produce a series of shots. This tends to be very useful to capture the moment whenever you need to. With the 20D however, the continuous shooting mode is so fast it is almost scary. 5fps may not seem all that big a deal, until you try it. Gently nudging the shutter button can easily produce 2 or 3 shots before you realize it. Again, incredibly cool, but also something to get used to.
The camera interface is also quite neat. It is amazing how many features Canon manages to pack into just a few buttons. That said though, some features are only available from the (well laid out) menu-system. It would have been nice to have had a second button (beyond the central setting button on the control dial) that could be programmed. I've got the setting button set up to switch between programs (colour 1, 2, 3 , B&W, etc.) by the way.
One strange choice in the menu system are the "custom functions". Instead of laying these out like the rest of the menu system, they are hidden under a single menu item. Selecting that gives you a selection from numbers 1 to 18, each with a specific setting. You have to navigate around them to find out which is which. This is harder to use then it needs to be and makes it look like an after-thought, which is too bad.
Image quality, as stated by loads of other reviewers ad-nausem, is excellent, even when using high ISO mode (800, 1600, 3200). Still 1600 and 3200 do exhibit some very visible noise, albeit less then on most other cameras. Whether you consider the noise-level acceptable, is, of course, a matter of preference.
Some other considerations: I've verified that the camera is totally usable when wearing gloves, as some other reviewers have stated. Very useful in this cold weather. It also features an orientation sensor, so it will automatically rotate images taken at a 90 degree angle. The AF assist is done through the popup-flash. It sort of strobes to help get focus. This is a neat trick, but quite a bit more disturbing then the more usual reddish light.
Summing up, this is an amazing camera. I was quite confident it was a good choice, but it still managed to amaze me on just about every level. The Nikon D70 might be slightly better value for money, but feature for feature you simply cannot beat the 20D.
One last note: I bought this camera in a regular shop. Comparison shopping on the internet revealed I might have been able to get the camera slightly cheaper, but in this case I got to take the camera home directly and got excellent service and helpful advice. My recommendation would be to do the same, unless the few extra bucks you will pay will really hurt you.