I didn't because quite frankly I'm annoyed at them. They, as far as I can tell, developed Latex-Lab at Google, an open source project, and abandoned it, but left it up as a stay-in-place advertisement for TeXniCenter. I have a very low opinion of those that start open source projects only to generate interest for their commercial offering. In Latex-Labs case, it is double bad, because they leave the open source, but abandoned, Latex-Labs server up as an advertisement. Actually Latex-Labs works ok for small documents, integrates with your google docs, and it is free.
Latex Lab