Windows 7 is a solid upgrade to Windows Vista and a revolutionary upgrade over Windows XP. If you are building a modern system, to get the best performance and greatest security, I recommend Windows 7 hands down. Windows Vista was actually a pretty solid upgrade over Windows XP, but some major security changes, somewhat steep hardware requirements for its time, and driver glitches plagued its user base in a way that left many with a bad taste in their mouth. With Windows 7, the security changes were mellowed to make things a little less of a hassle, the hardware available improved, and manufacturer support improved, making for a much better driver environment.

Anybody switching over from XP, keep in mind that Windows 7 (and Vista) use an improved security model, which does restrict things a little bit. While an administrative user is still administrator, there are occasionally extra steps required to make changes to the software. For example, if a program requires administrative access, at default security settings, you'll need to right click the program or shortcut and specify that you want to run it as administrator.

Of the three versions of Windows 7 available, I tend to recommend Windows 7 Home Premium for those who don't need more than 16GB of RAM and use it for general home use. It doesn't have all the extra bells and whistles, but barring a few specific circumstances, you won't need them.