PKV wrote:
3. ability to cope with rigors of MBA program (e.g. quant skills, ability to produce under pressure, teamwork skills, etc)
This one be careful about. Quant skills should come through via your GMAT quant score usually. Teamwork is almost always asked about. Each school has different opinions about what's important in coping with the rigors of their particular MBA program. The best thing you can do is to take the list of schools you are applying to and get a hold of the ref letter questions for each school to get a sense of what will be asked for and make sure your references can support the answers with very specific examples. Your ref should know your strengths and weaknesses and what you're doing to fix your weaknesses - this is almost always asked. In addition, if there's specific focuses for the school (e.g. more international, more technology, more finance, etc), then your ref ideally should know your work from that perspective.
Note that some schools ask "different" questions - like the wharton letter of rec in 2007 asked "How would you describe the applicant’s sense of humor?" - you don't want to be stuck with a referrer that thinks you're a wet blanket and can't take a joke, no matter how much she thinks you deliver like nobody's business.