CS6 Production Premium upgrade - any problems to delete old versions?

Question

Am looking to upgrade to CS6 from CS5.  However the CS4 full install original is still on my PC because I read it could cause problems with CS5 to delete it.
Have also read on these forums that all upgrades are full installs and that older versions can be uninstalled so long as I have an older version serial key number to use. 
Also that the Adobe registry cleaner should be used after an uninstall - but the Adobe site seems to be talking about using its "CS Cleaner Tool" after uninstalling pre-release versions - not purchased upgrades.
So Q. is can CS4 & CS5 be safely uninstalled prior to loading CS6?  (All Production Premium.)  And should the CS Cleaner Tool be used?
Does anyone have a definite answer on this please?  Naturally want to avoid keeping old stuff on the system if possible.
Haven't found a general forum for CS6 Production Premium.  Please redirect if not okay here. Mostly using PremierePro. 

Answer 1

I don't know what Adobe's 'official' stance is on this, and I'm not an offial PR spokesperson for adobe. I'm just trying to speak honestly about my own experice as a fellow user. If you're in a position to get rid of all your old stuff and start fresh anew then running an uninstall and a cleanscript is a good idea. I can't speak with authority on that because I typically don't use cleanscripts. I either restore to a clean OS image or just use the uninstaller. But I always carry at least one system with two or more consecutive versions installed on it. Having an extra version is no more obtrusive to me than the extra's GB's it occupies and I get a lot out of it because it lets me compare current behavior to previous version(s). Perhaps I've just been lucky, but I have been running multi-version software setups for well over 10 years now and as long as I'm using the actual released software I've had no conflicts. For the record, I do occassionally encounter uninstall-install component conflicts during a dev cycle, so I acknowledge they exist, but it's almost always due to an architectural change that was intentionally made to the installer during development.
We do extensive project upgrade and installer testing at each new release to ensure that you encounter no problems following wichever path you choose. We try not to assume that you will be running on an especially clean system, or an especially dirty one for that matter. But, there are only a relatively few of us testing these things in-house compared the thousands of users with unique scenarios that may generate problems we have not seen. I think Harm's (and others') point is that if you're in the middle of a big important project, why would you choose to upgrade software right in the middle of it and take that chance at all? I don't believe there is much risk there (assuming you're not jumping about half a dozen versions at one upgrade) but that still seems like common sense advice to me...