FWIW this is secondhand information from people who make that commute:
I have heard it is very difficult with many flights being oversold/ full. Depending on which airlines and their commuter policies it could cause quite a headache. Not sure if youre looking at regionals or something else, but all of the direct flights are mainline so dont count on a jumpseat either.
As far as coming in the day before- personally- this is the absolute worst part of the job. Unless you are single with no kids and no wife/ girlfriend at home, I would advise *firmly* against a commute that requires it.
Even if you are single it will get old as you forego one more night at home to sleep in a crash pad.
Not sure what your background is but airline life is different from many other jobs in that your time at home is 100% yours, but your time away is 100% gone. Im sure youre already in aviation so you are probably familiar with this but I came from a 135 operator that had fewer days off per month but more nights at home. I started looking into airlines because I was thinking "wow, 12 days off, no on call" etc. Its not quite as easy when you have to fit all of your life into your 12 days off- not only family obligations and general chores, but also a little relaxation time to protect your sanity.
Sorry for the rant, to answer your question, from my friends and acquaintances that make that commute, it can be tough, especially when winter weather shuts down new York.
Some commutes are easier than others- but if long term your goal is IAH then i would look at airlines with IAH bases and plan on moving to the northeast for the few years it will take to get enough seniority to hold IAH.