My 2 cents:
Unless you climb with your camera attached to your eye, you will miss many of these fast paced shots you are talking about (I think). Do you climb with people who are happy to wait for you to set up before they move on? I mention this because I initially thought similarly, but soon realised that by the time I stopped got the camera sorted out and started recording images, the moment had gone and I then had to pack everything away (holding others up) and move my butt.
Another thought is that although in camera metering may be very good these days, I don't think any of them (correct me here if I'm wrong) will handle high contrast snow/low winter sun conditions very well. Assuming you climb in the winter you will probably have to use the camera in manual (I know I do) to get the best out of it, which has immediately slowed you down again.
I am a Nikon man by the way. Does it show?
To redress the balance I will point out that the Nikon is probably significantly bulkier than the Canon. I know my D70 (with instant start up by the way!) was way bigger than the Canon 300D and my D200 is much the same. For me that is a winner because I feel if I drop the camera onto rocks it has half a chance of surviving, but you would be well advised to check each of them out in person. On paper it may not seem much of a difference, but carrying that weight/losing the rucsack space may not be acceptable for you.
Actually I think that was about 5 cents I gave you there. I'll need to shut up for a day or 2 now!
Steve.
PS you mentioned the second command dial somewhere. It does go some way towards speeding things up when you get used to it. The Nikon also has a layout along the lines of the D200, I think, which puts some of the main adjustments at your fingertips without having to scroll through menus. Not sure how the Canon is set up.
