I did this. We broke up within six months after 5 years together. The firm - though no longer a start up (the breakup juggled priorities and set us on the path

I did this. We broke up within six months after 5 years together. The firm - though no longer a start up (the breakup juggled priorities and set us on the path of a bootstrapped traditional firm) is still run profitably, nearly 9 years later, by us as cofounders. Both of us are now married to wonderful spouses. We found out that we were much, much better as business partners than we were as life partners. I don't know that I'd recommend it - but I love my life, and this is how I got here.