Just wanted to add my 0.02 in case it helps anyone out. I've lurked in these forums for the past week and have appreciated the helpful tips from those who have already took the GMAT
I spent a total of six weeks studying for the exam, while working 8-6pm Mon-Fri for each of those weeks. I probably got in around 18 hrs of study time per week, more or less. All of the material I used was from the Kaplan Premium Online course. My first diagnostic (paper) was a 620.
Diag scores were as follows:
CAT 1: 680
CAT 3: 710
CAT 4: 630
CAT 5 (UPT at test center): 730
GMATPrep 1: 640 (about 2 weeks before)
GMATPrep 2: 720 (1 week before test date)
GMATPrep 1 (reinstall, 24 hrs before exam): 690
I felt that the GMATPrep scores were the most predictive of how I actually did on exam day. Though, I actually didn't get much sleep the night before... probably fell asleep around 3am and woke up at 6am to go to the test... but still turned out ok.
If there are any questions I'd be happy to answer them. Good luck everyone!