The really only thing you need to get used to is the cornering characteristics of bigger wheels. They will corner a little bit wider, but bikes like the XTC and Cobia can turn very quick (Cannondale on the other hand is a different story...) One more thing is that 29ers can't accelerate quite as fast as a 26er, but it really shouldn't be a problem. Most shops aren't really even stocking mid and high end 26ers anymore.
-roll better/keep momentum
-get over obstacles really easily
-give you better traction (larger contact are with the ground)
-still corner nicely
-more stable due to the gyroscopic force generated by the larger radius of the wheels
-higher ground clearance so you can get over bigger obstacles