Elements has expanded remarkably with v.5.0. It is also available at a fraction of the cost of CS.
The learning curve is huge with either product, although, in my opinion, not nearly as frustrating with Elements as CS.
The argument has been tossed around that money should not be the deciding factor. If that's the case, I would highly recommend Elements for those of us who have never worked with photo editing software before. Get books, tutorials and study Bob Arlens superb articles. Then, AFTER you do manage to outgrow Elements, move up to CS. You'll have learned the basics and concepts without all the fuss of the full blown program.
Incidentally, both are available for 30-day demo downloads at Adobe.com.
Me, I've just started in U/W photography after being certified this past August. I'm quite happy with the results I get from Elements.
Oh, BTW:
PS CS2.....$650 list price
PSE..........$ 90 list price