There is a little bit of a difference in the FIRMWARE of the device, but not the hardware (not to my knowledge anyways). The only cosmetic difference is that some of the very early ones say 'Digidesign' on the back, mine would have said 'Digidesign' but that is covered with a sticker saying 'Avid'.

The firmware that makes a difference is '1.x.x' vs '2.0.1', firmware version '2.0.1' indicates it has the expansion pack installed (this is pretty much a NECESSITY to get as it adds better sounding amps and gives you the ability to load any preset, otherwise you'd be limited to pre-expansion presets).

As far as price, there are plenty of essentially new 11R's on eBay for about $350 (at least US eBay) right now, I guess a bunch of people buy the 11R bundle for $700 just to get full Pro Tools with an iLok 2 and then sell the 11R. These should all come with the expansion pack (firmware version '2.0.1') installed but it is always good to make sure you confirm this with the seller.

I get the feeling that Avid will discontinue this soon but that is just my feeling as they are now on PT12 and the 11R is only accessible via the rack editor now, that's why I bought a second..

Other power users, please let me know if I am inaccurate or left anything out. Hope this helps!