David Burnett talks to the New York Times on what cameras he uses and why he mainly shoots digital now - he's another Canon 20D user.  The article is interesting, but the audio slideshow is much more interesting.  He explains that he uses a number of different cameras depending on the type of photo he's going for and on the slideshow there's a few examples.

I love my 20D, but it's not a camera that I can use all the time, it's just too big, so I also have a Canon SD500 which I've mentioned before.  I'll get different types of photos from each camera; I can't do the same things with the SD500 that I can do with the 20D, but I can take it places a 20D just isn't appropriate.  It's hard to be inconspicuous with a large SLR camera and buy the time I've tweaked the settings the moment is lost.  The SD500 I use for more spontaneous photos, I don't mess with the settings, just accept the defaults and let the camera deal with the situation and most of the time it does a great job, probably better than I could have done manually.  Take this as an example - that was shot at dawn directly into the rising sun with the SD500 and captured the scene exactly as I wanted it.  The 20D on the otherhand lets me get photos like this, which the SD500 wasn't able to manage (subjects lit entirely by candle light on a moving boat).  The SD500 also shoots video, a feature I never thought I'd use as I've always prefered still shots, but I found a few instances when video captured a scene much better than a still image could.  The 20D as you'd expect from an SLR doesn't capture video.  Different tools for different jobs.

The New York Times also has some tips on digital photography, nothing really new to me there, but it might be off interested to any just getting into digital.