Pros
The work they're doing for people with rare diseases is great. For the employees who got in early enough to get stock options, they're probably going to make a fortune. If you are one of the favorite employees who can do no wrong, there probably isn't a better place to work. It really just depends who you work for, specifically.
Cons
If you are just starting and miss out on the perks of being there when the stock options were flowing before Vyjuvek came out, don't even try to get a fair salary out of them. The bean counters won't let them get away with paying anything. If you get stuck with a bad boss or some of the newer managers, it probably isn't even worth giving working there a shot. Honestly, I loved 90% of the time I was employed there, but the dynamic changed after the Vyjuvek approval. I would probably steer clear at this point. You could be at the bottom of the totem pole, one of the most senior people there with the most seniority, or just a regular, run of the mill, mid-level employee, and they will have no problem letting you go.