i can help you guys here.
I have already given GMAT once and scored 620(q:46,V:29)..gunning for 700 again next month. I had ordered 800score tests during my last attempt.
Take it from me, the quant sections of the tests are too easy(i can say easier than even OG). The verbal sections are very good. Replica of actual GMAT. I had scored 700+ in all tests(50+ in all Quants...even 60 in one). Its scoring system is also not up to the mark.
So my take is that, donot go for 800score tests. IF you are done with your practice stuff for Verbal , then u can order them and do only the verbal part.