Sailfish, you didn't mention if you were loking for gas or diesel. If your looking for a diesel would recommend staying with the 6.4 platform until the 6.7 is proven and we find out the truth on how long the urea lasts and how much it will cost, ect. ect. If looking at gas, then you might want to wait to see what the 2011's look like. Although smart money says the 2010 's will be reduced to make room for the 2011 lineup with some possible really good deals. As for the rest of the truck, when I upgraded from the 05 F-250 to the 08 F-350 dully, the swap from the 3.73 to the 4.10 gears was quite plesant. I lost a little mileage on the highway, but picked up mileage towing as well as sheer driveability over all (night and day difference towing) increased. I suggest getting the widetrack front end if you go LWB CC, as they are quite fun to park without it.
Just to add, barring the radiator replacement (under warranty, defective mounts, which were replaced) and an actuator for the ac/heat vents (again covered under warranty) 29,000 trouble free miles.