Not that I disagree with the recommendation, but how important is startup time really? Just leave the camera on when you intend to shoot. Or when you're turning it on, turn it on before removing the lens cap, putting the strap over your neck, bringing the camera up to your face and pointing it towards your subject. All that's going to take the better part of 2.5 seconds anyway.
Yeah, I don't see startup time as having any kind of bearing on a purchase at all. I start my camera when I'm going to shoot, then leave it on. I don't think I've ever been faced with a situation where my camera didn't turn on fast enough to get a shot.
Sorry for my delay in replying.
Overall, I think it has a lot to do with one's style of shooting, including the subject.
In general, I find that I turn my camera off "a lot", as it is the old school way of conserving power. Its probably not as important these days as digital cameras have become less power hungry, but as a result, I can shoot for quite awhile off of a single battery set because of less time burning the display, etc.
However, what it really came about from was from cameras that had "auto sleep" functions ... when waiting on a wildife subject for a particular behavior to manifest, an auto-sleep with a longer startup time = missed shots.
In general, I'll keep the camera on while I'm shooting a sequence, but when I'm changing to a new subject, or looking for a new composition, it might be only 15 seconds, or it might be 15 minutes. As such, my habit is to always shut down to prevent accidentally leaving it on, then once I find the next subject & composition, snap it on, fine-tune the framing and shoot.
Overall, I wouldn't have mentioned it, except that I did test-drive the 10D before buying my 20D and I noticed that for how I tended to shoot, the extra 2sec startup time was noticable. Perhaps a lot of it is that with wildlife subjects, I've learned to be very fast to raise, compose & shoot in order to get those "grab" shots.
...and if nothing else, when you're taking portrait photos of family members, they hate to wait.
-hh