I'm not a programmer, but I did TFA for three years in Compton after graduating with a BS in Physics. I would say that if you are serious about your start-up, it's probably not the best fit for you: you simply won't have the time or energy at the end of the day, especially in your first year. This of course assumes that one would do TFA because one wants to actually tackle the problem of educational inequality, and not just because one thinks it will look good on a resume someday or one has a martyr complex.
A typical day is: get to school at 7, plan, hold before-school tutoring, teach all day (with a lunch break of 30 minutes), kids go home at 3, hold after-school tutoring until 4, plan, go home at 5 or 6, eat, grade papers until you fall asleep. This was my experience at least.
I loved it because for me it was about connecting with people who had a completely different upbringing than I do. The skills I learned in the classroom have colored most of my professional life. I found that students, in aggregate, are excellent judges of character, and I really had to step up my game to gain their trust.
Common Criticisms and responses:
"It's crowd control..." -only if you're a lousy teacher (and there are plenty)
"TFA is a cult..." -it is, but after your initial training, which is actually very useful, you can choose to be as involved as you want (I wasn't very)
"Teaching is for those who can't do anything else." -Maybe there's some truth to this. I think it depends on what a person believes is important. Effective teaching in an inner-city school is definitely not easy, and to be honest, I think it's a problem in need of a new solution. I think the world could use a better model of education more than it needs a better way to use RSS to find out what one's friend had for breakfast. So if you have the raw innovative skill, it's a huge opportunity.