Beware there is some overlap between GMAT Focus on other products. Have you already purchased the GMAT Prep Pack 1? That is many more questions and a better value. Even though it does not give the diagnosis that quant focus is meant to.

I personally think that taken a full Quant section of a good prep test like the Veritas FREE CAT Test is perhaps more worthwhile. The Veritas test gives you lots of tools like "Easiest 3 questions missed" and "time allocation on last 10 questions."

If you do want to buy GMAT Focus you should post a question directly in the "ask the testmaker" forum and ask exactly what materials overlap questions with Quant Focus. If you have already used those materials it would not be worth it because even a few questions that you have seen before would throw off the diagnosis.

I have had a few students who used GMAT Focus before starting with me, and overall they were happy with the purchase. I do think David is right in that the free test will give you more feedback to analyze, so I would start there as well.

Thanks everyone for the feedback! I have decided to pass on the GMAT Focus and to purchase the additional CATs and practice problems.