We've installed the version 9.0, basicly, the steps we done were:
* Uninstall completly the old version.
* Do a custom installation if you are using IIS, the standart version doesn't create the virtual directories.
* The manager console has changed, so you'll set up all again.
* You'll need a administrator account for qlikview services (it must be add to qlikview administrators group)
I hope this help you.