EM residency is fantastic... The specialty is demanding while you're at work, but you only work short periods of time, and MUCH MUCH less than your colleagues on a weekly, monthly, yearly basis. It is VERY conducive to having a life, family, etc....
I am a PGY 2 EM resident and think it is great. I think it's much less demanding than med school. The RRC (residency review committee) for EM has also limited the amount of hours we work in the ED to less than 60 hours! So, unlike the rest of medicine, who is regulated by the federal mandates to be under 80 hrs/wk, we are cut off at 60! And all programs comply too.
But it's not all fun and dandy.... you've got to like what you're doing, and of course, you've got to take lots of off service ICU call your first year (where the 60 hrs/wk don't apply). And yes, you'll have to work many nights, weekends, holidays for the rest of your life. Most of all, make sure you like intubating/lines, working on your feet, being able to handle cranky consultants, seeing patients fast, and not having all the answers when it's time for d/c or admission. I am comfortable with this b/c I like diagnosis and treating based on clinical suspicion. Some people hate this (particularly your medicine types)... that's why they tend to be watchers in the ED instead of doers... they're waiting for the labs to come back b/c they're used to having them done when they're called. It is a different mindset. Plus I get to stay sharp on all types of clinical medicine... (at least the important aspects... the ones that your friends/family will want to know about when they have a complaint and worried if they are going to die).
My 2 cents... good luck