I can only speak to the department I worked in, and I understand things are really different for other departments. What I found is that it is a very collaborative environment and I can really trust and rely on my colleagues. Everyone is really professional and easy to get along with, and there is no drama. We are also working for a good mission.
There is unlimited time off and you can work wherever and whenever suits you. However, sometimes this make it really hard to truly unplug. The president is really committed to making sure that employees take time off, take vacations, and spend time with loved ones.
There is a lot of room for growth, if not within your position then in other departments in ASCO. However, sometimes growth/movement isn't as rapid as it seems it should be and that is always blamed on "HR red tape." I have seen a few colleagues get burned, badly.
There is a great culture overall and lots of great benefits. Staff lounge has free healthy snacks + lots of foods/drinks available for purchase.