In short: lower than market pay, longer hours due to inefficient processes, lack of recognition of your work, incompetence of the management, even outstanding performance does not guarantee you will keep your job or be promoted, every business client is unhappy with IS and they will make sure you feel it.
The work that's cut out for you is never about getting things done (let alone - done right, no one wants that), it's always about your boss pleasing his boss or some other boss somewhere on top. You are expected to work long hours, weekends and whenever else your boss feel like it, which usually comes with any IS position and is properly compensated by either good salary or telecommuting ability or more or less flexible work hours or some other perks. Not at Healthfirst, it isn't - the very boss that called you on Friday five minutes before your work week was over and personally asked you to work through whole weekend will never say 'thank you' on Monday - let alone offer anything in return of the favor.
If you take too many days off on a short notice - you run the risk being reprimanded (given a write up, letter from HR, bad review or being fired) for being unavailable and for bad performance. So plan your emergencies far in advance.
Most important thing to know is that you will NEVER improve your skills at Healthfirst. It's a good place to retire from, but AVOID AT ALL COSTS if you want to have a career or improve your skills by working on exciting projects. All systems and computers are old, obsolete and outdated, no one cares one bit about more efficient, tried and true approaches.
Many of the IS managers are promoted there because they sucked up better than anyone else around them, not because of their knowledge or expertise or contributions to the company. They can have zero management skills or abilities, may swear, drop F bombs and scream at their subordinates, but since they are their boss' gambling buddy or golfing partner or something else close enough - they are solid. Some managers are a pleasure to work with from a professional perspective, but those sink in the sea of incompetence and favoritism junkies. Expect those incompetent types to micromanage you down to every keystroke/communication/movement that you do. Given that seating is tight and you will literally sit with at least one person shoulder to shoulder if you work from the main office - your boss will either stare at your face all day long or will be seated behind you and will look over your shoulder.
Hiring process is very tricky - the interviews are conducted by managers only and the only people who have a chance to get hired are those who appear dumber and less knowledgeable than those managers at the interview. If you are indeed as desperate as to agreeing to work for Healthfirst - keep this in mind and don't shine too much on the interview, otherwise you will be seen as a threat to current managers and will not get hired.
Being proactive too much is frowned upon, you are expected to follow orders and praise your management for wise decisions, not question them to improve something (there's a separate department for that). Some of the process routines (the dumb ones) are forced by HIPAA compliance, the others (that are even dumber) are forced by incompetent senior staff, so trying to change that will put you either in possible violation of HIPAA (which is bad because management is so scared about those violations they will put you down in a second) or make you a personal enemy of some department director (which is worse and unavoidable and will put you down even faster).
Overall, IS at Healthfirst is not a good place to work at, it doesn't seem to be improving and at the current rate will most likely be replaced by outside vendors and contractors within a few years.