Windows 7 is apparently what Vista should have been.... or I heard someone else describing it as "Vista on speed, with a make-over"
I am currently on XP, but I am getting a new laptop sometime soon... unfortunately I ordered it about a week before they started putting Windows 7 in (I thought it wasn't coming out till February!) but I do at least get a free upgrade which I will be doing as soon as possible because I have sampled Vista on my sisters laptop and wasn't keen.
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Oh, and those of you still on XP, I don't think you can upgrade directly to Windows 7, you need a clean install. (I imagine if you put a W7 disc in it should explain what to do, but you never know)