Looking back at our timeline, we filed the S-1 about 3.5 months before the first day of trading. (I'd been there a little over 2 years before that, so well after it was clear we had a legitimate chance, but well before it was clear we could IPO.)

I would say that employees who were there right before or shortly after the IPO weren't all that different in terms of initial grants. The only difference is that pre-IPO employees could get ISOs which have slightly better tax treatment than NQSOs.

I would make the decision based on the work, the pay, and your overall feelings for the space rather than whether you applied 4 weeks ago or 4 weeks after IPO. You already missed the gains before the IPO, but most companies have a lot more gains after the IPO than before it.

If you're the type to be jealous that you missed on the pre-IPO gains, don't go, of course. Those employees who made "millions" in the IPO didn't do it because they joined 2 months before you. They probably joined 2+ years before you.