PhD, Startup, or Career? 
webwright: Do you have a sense of which one you'd regret punting MOST?  I can't imagine not getting a PhD gnawing at you for the rest of your life unless you love deep academia.I can't imagine regretting punting a job offer from BigCo, but people are different.The startup idea sounds cool, but making a better (or at least decent) mousetrap is really just an entry fee for attacking the sales/distribution problems associated with enterprise software.  Hopefully you or your partner are good at sales and eager to do it.I think most people are likelier to regret punting on a risky choice than the safe choice.