Elements certainly does 90% of what most photographers need - just check out a few of the tutorials in the magazines and on here - many quite complex things can be done in either CS or Elements (sometimes they seem to be interchangeable on those video tutorials.... they say it's a "Photoshop tutorial" for something and then it turns out to be all done in Elements. Just look at the current bunch of videos called "Teach Yourself Photoshop".... they're done in Elements!
My personal ideal combination would be Lightroom and Elements.... even if the "Organizer" features are duplicated in Lightroom. You'd still get to use both. "Organizer", by the way, is not even part of the Elements Mac version - so they'd need Aperture or Bridge, I think.
Biggest thing missing from Elements? It cannot do any editing (other than basic crops etc) in 16-bit..... a bit silly not to include that, as even Paint Shop Pro Photo can do it (and it's a tad cheaper). You won't miss it much most of the time, but eventually you'll get to a point where it's annoying not to have the capability. See this info at the excellent
Digital Photography School.