Recently I was helping someone out who has Vista Home Premium x64 and she announced "I want to upgrade to Windows 7". Now, I'm a Windows 7 Professional x64 user (99.9% happy) but I bought my computer with Windows 7 installed. (In fact, I have never personally upgraded any computer that I've owned except for going from Windows 95 to Windows 98SE.)
Even with running Microsoft's Upgrade Advisor it is my understanding that the upgrade process itself may not run as smoothly as one would like so I simply advised the person that "if it's not broken, don't fix it". All she needed was a minor fix for Microsoft Paint--a known issue with Vista--so I helped her out with that. I then turned off most of the programs that were running in the background and slowing her down and she had a nicely-running laptop again.
As a part-time PC troubleshooter I know the hours that it can take to solve annoying software problems. Most home or business users neither have the time nor the desire to spend time troubleshooting, so my advice to anyone considering an upgrade to Windows 7 would be twofold:
1. Run the Windows 7 Upgrade Advisor from Microsoft: http://windows.microsoft.com/en-us/wind ... de-advisor
2. Wait a bit longer and make your next computer Windows 8. It's only about a year away: http://goo.gl/rNqsh
If you still think that you want or need to upgrade now, do some research first online, especially for your particular computer manufacturer, to see if anyone has posted success/failure stories. And, as always, be sure to back up your data (don't rely on the Windows transfer process), make sure that you have all of your third party software installation discs, and check for driver compatibility for your peripherals.