I don't really use PS to its full potential, but I find the interface for LR better than that for Adobe Camera Raw. That said, I haven't upgraded from CS4, so I do know that the later versions of ACR have more functionality, but I think it is much easier to use in LR, plus there is the added benefit of keywording. I know you can also do that in Adobe Bridge, but I find it quite clunky and LR is particularly useful for batch keywording and captioning. I tend ot do all my keywording and basic processing, as wel las add any additional gradients that may be needed in LR, then switch to PS for the more precise and detailed editing. For example, the spot healing tool in LR is a real pain to use if you have to look over the whole image and while I still need to perfect my use of masks in PS, layers and masks are much better and I also do all my dodging and burning (wherei deem it necessary). In many ways, the most useful tool in LR is the batch metadata import preset.