I love my job and wouldnt consider doing anything else. Having said that though, it can at times be a very trying job- there is much more to teaching than meets the eye and you need to be prepared for that too, like the others said, prep, programming and marking can be very time consuming. There are also all the extra things that you need to think about some days you are a nurse, social worker, councillor etc. I work in a pretty togh school, so I find dealing with some of the behaviours and other 'home' situations to be quite stressful at times, but not all schools are like that- however you really do need to be prepared for the ones that are.
As for family friendly, at this stage in my life, I honestly don't think working full time would be very family friendly, there is no way I could do a good job at school and a good job at home if I worked 5 days a week, but being the profession that it is, there are great options for part time work. The holidays and the hours are a definate advantage in terms of family life though.
For me the job satisfaction I get, and the knowledge that I am out there making a difference for our future generations is enough to drive me on, so even on the toughest days I still wouldnt choose to do anything else.