Well, NVIDIA Surround has better bezel compensation support, is significantly easier to setup (in my experience) and is capable of doing DX10 and DX11 at resolutions of 5040x1050 and above, which the TH2Go cannot due to restrictions of the refresh rate in dx10/11. I personally can't think of any advantages of continued use of a TH2Go over Nvidia Surround, though there may be some that I'm not remembering.
The only one I can think of not having to use SLI in games that don't support SLI well at all (negative performance).