Pros
The New York office is very nice, on the 50th floor and overlooks Central Park. There are some nice people working in the office there and everyone has a collective feeling of sympathy for their fellow colleagues.
Kontras
You need to understand that if you join ION that you are sacrificing any chances of career advancement whatsoever. While no expense is spared when it comes to fancy offices, every expense possible is when it comes to employees. While starting salaries are reasonable, there have been no pay increases for years, and bonuses when given are tiny.
The CEO insists on a hands-on approach to every single part of the company (including approving an order for more coffee!) and the result is that very little ever gets done.
Benefits are awful for a company of this size (no 401k employer contribution, minimum contribution toward heath, etc). There is very little flexibility when it comes to hours or working remotely.
Think very carefully before joining ION and signing that onerous non-compete which could basically put an end to your career in this industry unless you change your industry/profession entirely or are happy to stagnate in misery at ION. I would strongly recommend against joining.
I would also point out what many on here have mentioned - there are a number of reviews below which are very clearly fake. If you read a review which jokingly refers to ION as a "Market Leader" or similar, you need to be aware that these have been written specifically to try and boost the dismal rating the company rightfully has on Glassdoor.