Hi all
Took my GMAT this morning and got 780 (Q 50/95p, V 47/99p)
First a great thanks to PG. I have been lurking for 3 months, soaking in all the info and energy. That's part of what prodded me into action. I had not decided whether to go for an MBA and I am still thinking about it. I'm 34, with a family, young baby, successful background as an exec in media and entertainment, an MBA would largely be a "future proofing" in case I outgrow my current activitiy a few years later. I certainly want to transition into VC/buy side at some point.
Finally I decided to act but could not find the right books which I had decided upon. Sachin_H helped me find them online. So I owe it to all of you to share what little experience I have so far.
I prepped exactly a month for GMAT. Forced August 25 because I wanted a crack at IMD, as it turned out, I did not go for IMD because Jan is too early for me to start.
Anything under 750 was not an option. Even though I know it is only one factor, this is the one thing I accidentally happen to be good at

I had a high GRE score 15 years (!!) ago.
After all the advice on PG and also my friend who took GMAT 6 months ago, I finalized the following:
1. Kaplan GMAT 800 - worth its weight in gold for people who are aiming in the top 10-20 percentile. Killer CR, RC, and decent quant.
2. Princeton Review - excellent Math review especially probability and geometry. I hate probability and combinations

Didn';t really do all the problem bins. I traded off practise time for test practise in my runup to GMAT.
I bought OG but dropped it immediately because it was too simple and also would have tainted my PowerPreps.
After a week+ of reviews, exercises in Kaplan/Princeton, I started tests. Working and with a small kid, I was very selective. I had all the old GMAT paper tests. Did two of them, made 800 and 780, realised they were not helping push me much. Found some old computerised Arco tests, they had no scaled scoring but I made on average 4 wrong in each section. Then moved to the two powerpreps, helpful for the computer environment. I even used a white board and marker to simulate the exam pad/sharpie. Soon abandoned it coz the smell was making me woozy
The best find was the GMATPrep two tests, I took them 2 and 3 days before my exam, made 780, 770, excellent questions and good practise. Two of the quant questions showed up in the real exam including - guess what - a Combinations one which I had gotten wrong in the GMATPrep ! For these, I made a point of waking early and doing them in morning. My appt. was at 9 am, so it makes a difference, everything from your breakfast to your state of mind, concentration and stamina matters.
Final evening, watched a cricket game till 11 pm (good relaxation), brushed thru Probability and quickly read the essay stuff in Princeton - I had ignored completely - but a 30 minute read helped immensely (don't have my AWA score yet though).
Must confess I had a little disappointment/greed at missing the 800. But I think it's OK for an old guy who took his GRE when Tendulkar was in his teenaged pomp, hammering the Aussies at Perth.
What lessons can you take away ?
Don't touch the OG when you start ! Finish the two power preps first because the computer experience is vastly more useful. And a lot of people may miss out the more recent and highly excellent GMAT Preps which is a 26 MB download from mba.com.
I think Princeton Review with its no nonsense approach to test taking, is the best.
Kaplan is the next step up. Go for it if you have a reality check and think you can attack 750.
You can't "mug" for GMAT (silly but obvious). In the preparation period, you may not hugely improve the English skills that God and upbringing gave you, too significantly. You can train your mind to spot patterns, tighten your game, and brush up your skills. In Math you can pay more attention to a selected set of problem types shorn of verbose proofs and formalisms which cluttered our school education. Again, you can tighten your game. I used to treat every mistake in Quant as a huge personal catastrophe and curse myself. Any desi from engineering should set the same standard. Losing points in quant is like taking points out of your pocket and throwing it in the gutter. Like throwing your wicket away against Kenyan part time bowlers in a selection match. OK, you've guessed I love cricket. You can learn a lot of life's lessons from cricket

Non engineers, it is still a very feasible section. DS is tricky but num problems should be flawless.
Now, I have to take some huge life decisions. One danger is getting carried away by all the enthusiasm on this board and blindly going for it just because it is within reach. MBA has to genuinely mean something to me and my family.
I also have to thank a post here (I forget whose) that I read way in the beginning. He said GMAT is not a formality but still it should be seen in the context of your other efforts. Don't lock yourself up for 6 months mugging for it. Make sure you have a balance. The other stuff - your introspection, applications, essays, financing, research on schools - all need attention. Don't get obsessed.
All the best, please let me know if you need any other info. Again, I must emphasise what a huge resource PG is, and what a wonderful thing web communities are. I felt their power for the first time here. Keep it up everyone. Maybe there is hope for us in the real world if we can be so open and supportive in the virtual one.