Some of the top end DSLRs can have a fair learning curve to them. I have a Canon 7D, ( also have had 20D, 40D and also have a 5DII), and it really needed a fair look through the manual and some tutorials to become familiar with some of the settings, the autofocus in particular.
This lends support to the old Chestnut about never going on a vacation with a brand new unfamiliar camera, it is too easy to get settings wrong for a photo event that really matters.
GG's point about a 550 or equivalent, if the costs are about the same is a good one.