I bought a new computer in November, and got stuck with Vista. I have the Home Premium edition (don´t know what the difference is between basic and premium). I still prefer XP, but when you get the hang of Vista it´s quite ok (about as ok as anything Microsoft can ever get...), except for the stupid amount of memory it uses.
When running UO, I was going nuts at first, since I was totally unable to patch, but solved it by (like Kimi said) running the program as administrator. However, the change must be done by right-clicking the exe-file (I thought I could do it from the control panel, but that didn´t work). Now I have no problems running or patching UO, besides an annoying message that pops up every time I try to log in, which informs me that a possible threatening program wants to access the internet, will you still allow it? Yes, and please don´t remind me again. But it will. Every single time.
Edit: However, I´m a very "basic" user. Have never tried to modify files etc. If you´re interested in doing that I have a feeling that Vista would be very... problematic.