I was a GRPN employee at IPO and I can confirm that even with your stipulation, it sucked.
GRPN and TWTR are not the same. I can assure you, that things worked out just fine for GOOG employees. GRPN was very clearly broken. TWTR is not. Whether it is worth this or not I don't know, but I wouldn't expect it to behave like GRPN.
No, it sucks to be an employee because it is possible that a material part of your wealth is now in a casino, your tax liability just matured, but your ability to pay for it is riding a train with a potential to crash, and all you can do for the next 180 days is watch.