I tried it today, and I got some problems...
...and after spending an hour, trying to solve the problem, I went back to 7.5.
I'm on Vista here.
This is what happened...
Just to be on a safe side, I created new Restore Point.
I uninstalled 7.5,, restarted computer, and went with 8.0 installation.
At first, I got a warning about another AV present on my computer.
What the heck?
I thought, maybe AVG was complaining about ThreatFire, so I stopped installation, uninstalled TF, restarted computer, and tried to install again.
Same warning.
This time, I went ahead with installation, and I had another warning about AVG not being able to initialize Window Firewall (which I don't use).
I disregarded this warning, as well, and finally AVG said, it was installed successfully.
But, when I tried to run it, I got this:
The application has failed to start because its side-by-side configuration is incorrect
I did a lot of search. Someone suggested uninstalling Visual C++, which I did.
No dice.
Finally, I got tired of this crap, and I went back to 7.5
I may give it another shot over the weekend. I suspect, 7.5 left some leftovers, which were screwing 8.0 installation.