Vista as User - What Works / Doesn't as a User Account

I'm considering reformatting my machine and setting up two accounts for myself:  One Admin account to set up the machine, and then another account as User which I'll use for day-to-day use.  I know some functionality in the NIS2009 console are unusable in User mode (or were during beta).

 

Is there anything from a security perspective that WON'T work if I run as a User on Vista (64 bit)?  

 

Last question is not NIS specific:  Is this overkill, given User Account Control should protect my account even if its an Administrator?  Do I go as far as changing the "hidden" Administrator account password as well?