I just finished grad school and undergrad right before that (I lumped them together in 4 years; not to brag, this matters for what I'm about to say). I spent most of undergrad tempted by a few nibbles to take a gap semester or year and see what happens. The way I see it (and others on here may disagree with me), you should stay in school unless the golden opportunity comes along. Here's why: you are earning your education at one of the top schools in the world for EECS. You, provided you don't screw up, will have any number of opportunities post-graduation that others won't have, especially when it comes to startups. I graduated in 5 semesters from undergrad because I wanted to 1) go deeper into a technical background (undergrad in information systems / business - yes, I'm from "the dark side") during grad school 2) work for a startup

I chose to go to grad school, and along the way wound up working for a healthcare informatics startup. Great team, I trusted them a lot, even when they had a major product pivot. Last fall, I had to make the choice, wait for a spring offer to join them full time (yes, please and thank you) and reject other fall offers, or "play it safe." I took the handshake agreement and it wound up falling through. Am I pissed? Yes. Am I glad it happened? Well, I got a great learning lesson out of it, and am now doing my own startup in data analytics, commercializing a side project I did during grad school.

What I'm trying to get at is that yes, you will always regret the "what ifs?" However, be rational about the team, the product, and the vision, and the opportunity cost of putting your education on hold. Yes, you can always go back, but I've had friends do it, and it is hard(er). I'm happy to talk more about this or follow-up, since I know from semi-first-hand experience a bit of what you're going through. You have a lot of options on the table, but just look long-term and be true to yourself, more than anything else.