One thing you've probably heard about Vista is that it needs a significantly more powerful PC to run than Windows XP. That's not exactly true, and Vista should run on pretty much any PC bought in the past couple of years.
That said, Vista is far easier to use than Windows XP, it's more secure, looks neater and is pretty much everything we'd hoped for in the next version of Windows. Just make sure you get the Home Premium Version rather than the horribly cut-down Home Basic.