Why not check the "Additional Plug-Ins Folder" in Preferences > Plug-Ins in PS? That way you could install your plug-ins whereever you want once. Especially when going from one version of PS to another. You don't need to reinstall them ... just point and restart PS! You can even have any other graphic software (like Paint Shop Pro) point to that same folder.

I created a "Extra Plug-Ins" folder. Inside that folder I created sub folders for each plug-in (Alien Skin, Eye Candy, KPT etc...). I installed my plug-ins into those sub folders. I point Photoshop, Paint Shop Pro & Photo-Paint to that "Extra Plug-Ins" folder. When I went from CS to CS4 I just checked that box in Preferences and browsed to my "Extra Plug-Ins" folder and Voila! all set with no pain the butt plug-in reinstalls.