So UAC is how to make an OS more secure? Placing the responsibility on the user for choosing between "Cancel" or Allow" to protect your system is not the definition of security. Granted, there's likely to be a bit of spirited MS-bashing (this is a Mac forum, after all), but if it was a matter of simply badmouthing another OS, where's all the Solaris disrespect, or the trashing of Linux? Nah, MS deserves it for the most part.
Years overdue, missing all the major components that were the keystone improvements to XP, requiring most average users to upgrade hardware or miss all the GUI-goodness, six freaking versions, and major corporate and edu IT staffs refusing to get anywhere near it forcing MS to "allow" OEM XP builds for an extended period. Whew. Not a successful release, in anybody's book.
UAC covers more than constant nag screens when you're running as Administrator like most people do.
It's because you're running as administrator you get more nag screens - because Microsoft, probably rightly given the reaction from the masses and certainly here, thinks that you're too dumb to consider the security implications of running as Administrator.
Set yourself up as a Standard User and you'll find the experience much more OS X like. If it needs permissions, it will ask you to present yourself as Administrator.
The reason that MS gets much bashing is that Windows is probably the only other OS apart from OS X where people who don't have any clue what they are doing can pick up and use on an everyday basis. And in many ways, it is certainly less forgiving of ignoramuses than OS X.