I was getting a bunches of blue screen's of death on my personal HP TC2114ca which is a neat little table pc, amd64 with a nvidia graphics. I got it cheap after HP refreshed the model with amd64 and ati graphics ( a logical step once amd bought ati).
It came with 4gb ram and 64bit vista.
So i decided to fix it by putting windows 7 on it.
Did the painless install/upgrade and it just worked. My touch screen works but my fingerprint reader and fancy hp keys don't. HP says wait for october 22nd.
But it works.
It seems faster but the vista version wasn't slow.
I really can't see much of a difference other than changes to where stuff is in menu's and control panel.
It does seem to fix the big problem with vista - perception.
Now granted this is a big hardware system so i can't comment on performance of windows 7 vs vista on wee netbooks or older less performant hardware but then why bother upgrading any of them. Just use the OS them came with. Networks are now under $300 so spending over $100 for a windows 7 upgrade seems a waste of money.
Just buy a new OS when you by a new system. Spend your money on a new mouse or some cool software or a higher speed internet connection or an big external hard drive. The last two will get you more than an OS upgrade will.