I have taken 3
MGMAT CATS and performed badly in the quant simply because i find their questions very time consuming and then i run out of time so I have to guess at least the last 5.
I tend to "fight" some of their questions in the 700-800 range, and get half of these correct (spend way too much time on them) or spend 1-2 mins and guess and get wrong. The thing is I do not let that get me down. It just a matter of practice.
My highest Quant score on my 3
MGMAT is 45, lowest is 38. I have done GMATPrep1 and scored 49 on the quant.
So bottom line, use
MGMAT quant to learn concepts (their explanations are excellent), and use it to do some really bootcamp type CAT training, since it is tough.