I have not bought from this guy, but he seems to be good. The whole ebike scene is pretty new so not many people have much of a pedigree.
Anyway, he sells the Bafang mid drive, which people say makes for a very sweet conversion. You can buy it cheaper direct from China, but his are custom-spec'd and tested, and he is reputed to stand behind them. Whereas buying direct can be a real problem if there is an issue.
I plan to build a Nova Downtube folding bike with one of the Bafang mid drives:
http://lectriccycles.com/collections/all