Can't speak for CS4, But I recently did a reinstall of my Photoshop CS3 and it seems to be working alright. I also downloaded the Lightroom 3 beta and it too seems to be working without a hitch.
I am running win7pro (64 bit)
I started a thread concerning Lightroom 2 and my clean install of Windows 7 and the "easy transfer" method of migrating data back to my system. My concern is do the LR catalog files need to reside where they use to prior to the upgrade? Or will LR2 see the cats as it is being reinstalled?