I have noticed one definate benefit Vista's UAC brings to developers: allowing them to work as an administrator, and explicitly notice everything their program does that a regular user can't do.
Often times, software won't run as a non-administrator because developers run on their own machine as administrator and see nothing wrong with the concept that their user would do the same. Now, with UAC, the developer can still run as administrator, and if they leave UAC on as I have at work and at home, they can really appreciate how many actions a normal user simply cannot perform. The result: vista has given a heightened awareness to some developers about the rights required by their code.