I purchased a laptop w/Vista, just before Win7 was released (I go the free upgrade). My desktop was running XP (it died shortly thereafter, and my new desktop came with windows 7) I didn't upgrade the laptop until after I used the Win7 on the desktop, so I could see the differences.
Windows 7 is good, and makes for very easy file & printer sharing in a home network.
Just be sure you know that Windows 7 does not come with an email program installed...no Outlook Express, you will need to download an email program....so be sure you have all your passwords and mail server setting written down before you upgrade.
I'm using Mozilla's Thunderbird email. Microsoft recommends Microsoft Live.
I never had a problem with Vista, but I only had it for a short time. But so far Win7 has been very stable and I've only had minor compatibility problems with my old XP programs.
Fortunately, my old XP hard drive is fine, the motherboard died, so I was able to transfer the important programs and data.