I’m still on Vista and running Windows 7 on another partition but I didn’t get around to move all my data and programs.
But from what I’ve tested I can recommend Windows 7. Especially over Vista.
If you’re going to buy a new laptop anyways and you could choose witch one you get, then Vista would be a bad choice in my opinion. Microsoft is not going to support it for very long due to Windows 7’s success.
And 7 is faster and more stable then Vista.
So unless somebody can come up with a good reason to go with Vista I would go for Windows 7 whenever you can.