Hi Greg ..
I'm not sure.. LR3.2 installed into its own program folder so its not nuked the original which is good. With the CS .. I always thought you could just drag and drop the new ACR into the plug ins folder and then when you open up a RAW CS gives you the option of which version of ACR you want to use. I could be wrong.
So far .. the one or two files I've touched this evening.. the detail looks a wee bit better and sharper than before, seems to pull just that wee bit more out of blown highlights (not by much though). To early to judge but its the only app so far thats been making my Corei7 run at 60%+ on all cores !