The first time I took the GMAT I only self studied using the GMAT official guide and I was able to get a respectable 670 (Q49 V33). My main weakness was the way I approached quant (too much complex maths and I wasn't fast/efficient enough on most standardized questions), and on the verbal side I lacked a proper strategy (I had the bad habit of not properly eliminating answers and just selecting the one I though that fitted the best)
EMPOWER was a huge game changer. I knew that for my second try I had to take a good, structured course that would go through all the core content and specially teach strategy regarding elimination of wrong answers.
EMPOWER definitely excels at this last topic: its triage tips, and strategies specially for sentence correction, allowed me to improve 30 points (all in verbal, going from V33 to V37)
I would definitely recommend this course to anyone. The only positive criticism that i have is that I believe it lacks a bit more difficult excercises (700+) on the quant side.
Thank you very much EMPOWER for my 700 GMAT which has allowed me to gain admissions at Kellogg, INSEAD and LBS!