There's some useful functions in the full version of ACR not least of which is the spot removal tool; the ability to have a fully cleaned up image (i.e. all dust spots removed) at the RAW processing stage is a real boon and reduces the need for additional layers once inside Elements.
What I'm about to say next may well be common knowledge but I can't recall having read it anywhere or heard mention of this little trick: you can access the FULL version or ACR through Adobe Bridge! Deep joy! Bridge is used as the library function in the Mac version of Elements as opposed to the Organize program, which is used in Windows versions.
It's simple to access, too. When you're organising your library in Bridge simply select the RAW image you want to process and click on the icon on the toolbar (top row of icons) that looks like a lens diaphragm, which is second from the right, and the full version of ACR 5 will open. You can also open JPEGs, TIFFs and other supported file formats in ACR 5 in this way.
So, if you're a Mac user and running Elements 8 with Bridge you get the real bonus of the full ACR program. Hurrah!
Just another great benefit of being a Mac zealot...