Upgrade Vista to Windows 7 Ultimate

I just completed a successful upgrade as I did not want to loose anything on the computer. The only item that had to be upgrade as well was a .net feature and then it went quite smoothly. Now that it is complete I am looking for the Wow factor but don't really know what to look for as the desktop is the same as before except for the Status Bar.

1. What might I notice different from the upgrade vs a clean install?
2. Can I Crash everything and do a clean install later?

Thanks!

What might I notice different from the upgrade vs a clean install?

Visually nothing. Depending on how "healthy" your windows vista is before the upgrade, you may notice various minor issues.

(Windows 7 Performance Check: Upgrade Install vs. Clean Install )

Can I Crash everything and do a clean install later?

Yes, you can if you have the windows 7 installation dvd.