The Ultegra 6800 (11s) has been redesigned and has a lot of improvements on the old 10s versions (105 5700 or Ultegra 6700). Aside from the obvious additional cog, the most notable are the braking and the front shifting which uses a longer arm on the FD for a lighter shift action.
For $350 I'd take it. It's a pretty sweet deal. For comparison, ChainReaction has it for $872.