CS5 has some great enhancements in it. The noise reduction has been nicely upped amongst other things.
Dont buy into the "get LightRoom 3" thing. Its a good software, but if you are used to photoshop, stick with it. The bridge software is pretty much as powerful in terms of image manipulation as lightroom 3...same sliders, more or less same workflow. It is missing the file sorting and structure LR3 has, but it can give you what you want for quick multiple edits, staying with Photoshop for the heavier work.