690 (Q46/V39)- Should I retake??

I first attempted GMAT 2 years ago when I just completed UG without substantial preparation inorder to see what the fuss was all about.I had a score of 640.

For the last 2 months, I have been preparing for the GMAT (2 hours a day on average). I used Kaplan premier and princton review:crack the gmat (the book's overemphasis on guessing is really annoying) for the fundamentals and torn through the 12th official guide (literally...the book is now in shreds). After these I took the GMAT prep and had a 710 and a 700 on the practice test. I was content as I felt that a score in the early 700s would suffice.

So last Saturday (18/9) I took the real test. Used a template for the AWA and felt that it went okay. However, 30 seconds were deducted from my time in quant. because I did not activate the timer on time (I left my system for the break which I thought was still 10 minutes). This put me in some kind of extra pressure during the quant. and I eventually had to guess on the last question ( I knew how to get the solution but with 30 seconds on the clock I could not take the chance ofnot finishing;if I had the 30 seconds I lost at the beginning I would have gotten the question and perharps gotten a 700 which sounds much better than 690).

Then I started the verbal section. I may have rushed it a bit as I did not really read the comprehensions and was mostly looking for the answers to the questions asked. I had 15 minutes left when I was on question 41. I choose what I thought was the answer and went thought the additional stuff at the end of the test hoping to see like a 710. Then I saw a 690 and my heart sank because I may have to rewrite the test at a later date.

I have been discussing with people. While some say that the score is okay. Some say that its better to retake the test and exceed the 700 mark since I have time. But I am not sure if the efforts required to achieve that is worth the extra 30 points on my current score.

So what do you think.

The school I am currently considering are;
INSEAD- My number one school=>gunning for the Jan. 2013 marticulation
Wharton
London Business School
Chicago
Columbia

My present profile.
23 M African (hope diversity is in my favor )
My academic work at UG (Accounting) and graduate school (Accounting and Finance) are very good but not great.
1 year audit at Big4

I am hoping to switch to investment banking or PE/VC post MBA. Do people trying to switch to PE/VC concentrate on entrepreneurship or finance or both at B-school? I am hoping to have part completed CFA when I apply and aslo to be much better able to articulate my expectations post MBA.

And I have heard that post MBA, potential employers may use GMAT to screen potential employees. How truth is this?

Finally, what should I try to achieve in the next two years to be more competitive when I apply and how important are extra-curricular activities to being accepted to top MBAs.

I have gained good insights from this forum. Thank you.