One extra reason to be careful before you spend your money on GMAT Focus: there's some overlap between the GMAT Focus question bank and the official GMAT guides. There are at least six GMAT Focus questions that also appear in the Quant Review guide, and more than two dozen that appeared in the 12th edition of the GMAT Official Guide. There aren't as many overlapping questions in the 13th edition, but you probably won't be happy with GMAT Focus if you used the 12th edition. But even if you haven't touched the 12th edition, you'll see a few repeats... and that's pretty frustrating when you're paying $1 per question.
But other than the bizarre length (24 questions), the incredibly large score ranges, the ridiculous price tag, and the repeat questions, GMAT Focus is pretty awesome.