Microsoft are due to replace Windows Vista with a new version (Windows 7) in October this year.
If you dont need the PC urgently it may be worth wating till October and get Windows 7.
If you need it now, then Vista will be fine.
Vista has had some terrible press, but I dont believe it has deserved all the bad press it has had.
I have to say I prefer XP to Vista, but buying XP now, 2 and a half years since Vista came out, would not be a great idea (due to support issues, fixes and so on).
You can easily add more USB ports to a PC by buying a USB adaptor.