Forgive me for completely disagreeing here, but no you DON'T have to turn off UAC under Vista as I use Vista64 just fine with it on for all programs I run. (Saitek drivers, Hyperlobby, IL-2, COD, EQ2, LOTRO, etc...) And no I don't get UAC prompts all the time due to following the below rule.
I agree with not installing under C:\Program Files as that is considered a protected area under Vista and any program that is not written for Vista should not be installed there. C:\My Program Files would be a good place if they only have one drive. This one thing is 99% of peoples problems with running games under Vista.