I took GMAT today and scored 720!
PowerPrep 1 - 640 after doing some OG
PowerPrep 1 - retook the test and got 710, but a number of questions were repeats
PowerPrep 2 - 660 (was very disappointed, because I finished most of OG and felt that I was doing pretty well)
800 score - 560 (ouch!)
PowerPrep 2 - 710 (did this test after a month or so after the first attempt and did not run into any questions that I could remember. I think this was pretty representative of real score)
800 score test 2 - something around 600+
GMAt Papertest - 720
Princeton Review - taken 3-4 days before the real test, scored 680
GMATPrep - found old versions of the test on the internet, scored 710 on the first test and 750 on the second, but quantative seemed too easy and verbal had a lot of repeats.
Conculsion: if you do not get 700 in PR or 800 score, don't get discouraged!
It's still possible to get 700+ in the real thing!