Hi wiredgirl
Over the years I've had roommates and close friends who were residents (FP, IM, Psych and Surg) and have observed the following:
FP and Psych definitely seemed to have the best hours and often could take call from home (this will vary from program to program)
IM and Surg definitely had the worst hours, fewer days off and fewer days coming home early post-call.
Once when I was rooming with a Psych and IM residents, the IM resident calculated how much he made per hour (since they were in the same program they made exactly the same): he earned less than minimum wage while the Psych resident earned a fair bit more (not a great bit more). Since he hated IM anyway, this resident ended up switching to Psych and lived happily ever after (not really, but makes for a nice story).
Anyway, these are just my observations and I'm sure a resident in those fields can give you more definitive information. I'm currently applying for surgical programs and the estimated hours per week ranges from 65 to 96+, with vacation time ranging from 10 days to 3 weeks. I would suggest you check out the following for more information:
www.medschool.com - has forums and other information on all the major specialties under med student location
www.ama-assn.org/freida - you can look up specific programs and get a feel for how much vacation time, on call hours and hours per week are given (this is supplied by the programs themselves and is not guaranteed to be accurate in all cases)
I'm sure the American College of Physicians and College of FPs also have web sites which can give you more details on the lifestyle. The bottom line is two-fold here:
1)FP and Peds typically have more family/lifestyle friendly programs
2) if you enjoy what you do your lifestyle will also be rewarded as well.
Best of luck!