I've been using LR3 since the first beta came out, and upgraded to the release version as soon as it became available. I am very happy with it. To me, the tools have improved greatly (noise reduction being one of them). They have added a lens correction panel that can automatically or manually correct for lens aberrations if you need to. If you do a lot of printing, they have added picture packages. I haven't played with those, so I can't give you a lot of detail on that. They have improved the vignetting tools and also you can now add grain if you want. And there is more. I would recommend downloading the trial version of it before you make your decision. You don't have to uninstall LR2 in order to use it, and LR3 will create its own catalog so you won't be overwriting your LR2 catalog by using it. I've been an LR fan since LR1, and have upgraded every time so far.
As for CS5, I upgraded to it from CS3. I don't use CS as much as I used to since I am getting better at LR, plus I don't do all the fancy, creative stuff to my photos that some people like to do, either. I am more interested in the basic stuff of processing, and occasionally removing items (like power lines, poles, etc.) that get in the way and you can't always change perspective to avoid getting them in the shot. To me, the improvements in HDR processing in CS5, and Content Aware fill for some of the work I like to do were reasons I upgraded. Plus, I went from a 32 bit version to a 64 bit version, which has improved performance. And upgrading my processor to a quad core from a dual core has also helped. CS is one program I won't upgrade every time. Depends on what the offering is. There are others here that could probably give you a better overview of CS5 than I can.