So, the specific complaint I read here is about the User Authentication dialogs? That basically pops up when an application tries to modify a file that's not in a standard place for that application. This generally reflects an application that doesn't follow long-standing Microsoft programming guidelines, and is a useful way to keep any malware accidentally on a machine from hurting anything.
That said, it's also trivial to turn off on a particular machine if you're not worried about misbehaving apps and malware. The good news is that the existance of the UAC is finally getting developers to follow the rules and newer apps don't trigger them nearly as much. So if that's your primary complaint, you can either turn it off if you can live with XP-level security, or see if your apps have been upated so as not to trigger that.
Which version should a video editor buy? I think any of Home Premium, Business, or Ultimate would be equally good for runnig the apps themselves. Business and Ultimate gives you full domain and remote desktop support if needed (not for a home machine or standalone workstation), and Home Premium and Ultimate give Media Center (possibly useful for testing content playback). As to why diffent versions? The same reason that most software products have different versions; there are features that Pros are willing to pay for that consumers aren't. If you have a single product with a single price, either the price is too high for consumers, or so low that you can't justify bulding in Pro features for that market. Again, most content creation products have a varient on this (three versions of Photoshop, 2-4 of Final Cut (depending on whether you count the server and iMovie). Note that XP actually has quite a few more available versions than Vista:
http://en.wikipedia.org/wiki/Windows_XP_editions
http://en.wikipedia.org/wiki/Windows_Vista_editions
In the end, for consumers you basically have the Home and Pro versions like XP, plus the Ultimate version that combines all the features of both (the lack of which was a pain for me at least, since Icouldn't be on a domain and also have Media Center).
Ben Waggoner
Principal Video Strategist, Silverlight
Microsoft Corporation
Compression Blog: on10.net/blogs/benwagg/
Compression Classes at Stanford and PSU: on10.net/blogs/benwagg/21622/
