Upload & Sell: On
ACR (the technology behind both PS and LR) was significantly improved in CS5 and LR3.
Unfortunately, this is one big reason to use CS5. Comparing the two, if you do anything else besides some image manipulation, I can't recommend LR over PS. The number of things you can do in LR that you can't do in PS (better crop overlays, consistent history states) don't come close to making up the difference.
I have both, but rarely use LR; there's no reason to when you have PS. The number of advantages, including layers, when using PS are literally too large to enumerate here. LR is cheaper (and should sell for $99 retail IMO), so if that's the most important factor, buy it. Otherwise, use PS.