Stacey Koprince wrote:GMAT Focus is a GMAC product - it's new (launched in March or April), but it's from the official source.

I've mostly heard good things so far about GMAT Focus - it contains the most recently retired real test questions, and the test includes some basic explanations (better than GMATPrep!). It also gives you some analysis about your performance in different areas.

Some people have thought it was a bit expensive (I think it's $25 for 24 questions). Certainly you can get many more questions for the money from OG. Check out www.gmatfocus.com for additional info.

Agree with bilko on the paper tests. Fine for practicing individual questions or putting together your own sets of questions, but don't take it as a full test and expect your CAT experience to be similar. The structure and scoring of the two tests are very different.

Stacey Koprince wrote:GMAT Focus is adaptive, so the difficulty level you experience will be whatever you can earn while you're taking it.

Multiple sources have told me they think GMAT Focus is on the harder / more sophisticated side than OG (again, if you earn them). That was my experience as well.

So, I'd say:
1) don't do GMAT Focus at the start; wait till you feel like you've made a lot of progress
2) make sure you're well-rested and ready to BTG! when you sit down to do a GMAT Focus section