Definitely a buy!

After the official material that is provided by GMAC, these tests are the best indicators of GMAT performance that I have come across. The results that are projected by these CATs understate you true abilities by a small margin generally but the analytics that come along with them is priceless; they allow people to drill right down to the sub-topics that need work and can help people identify weak spots fairly quickly.

Having said this, I would also like to state that the quant section on these CATs are lengthier than the actual thing, not more difficult but longer, so time management is critical in these CATs.

I would certainly recommend these CATs to anyone aiming for a high score!