Elements and CS5 are very similar. The transition is easy to make.
If you can get CS5 Extended Student Edition for only $199, I say get it.
Elements has so much less capability compared to CS5.
The Camera Raw Elements has is heavily de-featured compared to the Camera Raw CS5 has.
There are just so many features and functions CS5 has that Elements doesn't. I used to say Elements had 85% of what CS had, but on closer examination I now say that Elements has about 30% of what CS has.
The biggies are: Bridge, 16-bit edits, better selection tools, easier masking, more options for layer styles, more options for background selection (I just learned about one I didn't know CS5 had, thanks to my NAPP membership), more agjustment layers, more Curves and Levels options, more tools, and more.