plsubbu's points are great and they match what I would have said. My GMAT was not that great and I almost gave up. However, I managed to write good essays. The Admission Dir mentioned in the Orientation at Kellogg that she rejected someone with a 800 GMAT score.
I spent a lot of time writing my essays, getting it reviewed by friends doing their MBAs, and then rewriting them. It was frustrating and it sometimes I got mad at the school
but I stuck on and it paid off. I agree with plsubbu, the essays are the heart of the application. Read and re-read the essays to make sure the logical flow is correct.
Reco letters are very important, I wrote mine myself in differing styles with different aspects covered based on who the recommender was. Both are my supervisors, one at the Project level, other at the Dept level. Then I gave them each a "Talking points" list with my work achievements on there. The Dept Manager has an MBA from a top 5 school, so I made sure he mentioned that. Adds credibility. The Project level mgr has an MBA from a smaller school. For my GSB Chicago app, I asked a friend to write for me, he is currently a GSB student. If a current student says "I am current a student at XYZ Univ and I feel that Mr ABC has all the skills needed", it looks really good.
I agree with the last subbu's paragraph also. I wrote my essays and then interviewed. After the interview, I finetuned the essays and submitted.