I've used Windows for years. 98, 2000, XP, Vista, 7, you name it. Windows 7 is by far the quickest, most reliable, and most pleasing operating system that I've used in a long time. I highly recommend it.
It's a nice OS, but I wouldn't recommend installing it on anything and everything out there... you do need to be careful. Firstly keep the requirements in mind, for old computers on or around 7's minimum requirements I'd still recommend XP (it's inevitably pretty sluggish with these types of boxes.) Again, drivers are another thing you need to look at (as mentioned above), we've already had at least one person posting several threads complaining about the lack of drivers for a wireless card.
That said, if the drivers are around and you're running Vista currently, 7 is a far better OS - I still maintain it's what Vista was really meant to be to start with.