I'm using LR4 and I'm really happy with it. Compared to DPP, that I've never used, LR has this cataloging, collections, published collection... and many others features around the develop module. The latter is quite amazing IMHO, especially the latest process (process 2012).
AFAIK, Camera Raw in Photoshop is the same engine as Lightroom (I.e. Lr4 = Acr CS6); correct me if I'm wrong.
I have no idea about the quality difference between the two tools (DPP and LR) but I'd be interested to see some tests.