For me to get the most out of the Lightroom 4 beta, it would be a tremendous help to be able to take a file from the Develop module and open it in CS5 as a smart object, preserving the possibility to tweak it subsequently in Camera Raw. It would be nice to have a time-limited beta version of Camera Raw 7 that functioned in CS5. I'm sure that this request has been made elsewhere, but at the risk of repetition, I wished to voice it anyway.
There is much to like in the Lightroom 4 beta. Soft proofing is great. Would be nice to have the option of Curves functioning in the usual way as it does in Camera Raw 6 and PS.