I think it really depends.
If you work as a critical care doc in the community, there is a huge trend of moving towards shift work. It would be similar to the current lifestyle of an emergency medicine doc. Plenty of time to see the family. $$$
If you go into academic medicine as a p/cc doc it also depends. If you plan on being a clinical investigator, you will most likely attend any where from 2-4 months per year. The rest of the time will be involved in either basic science, clinical epidemiology or health policy research. You'd be expected to be independently obtaining grant support to pay for a portion of your salary. You can do this as solely an intensivist or you can do this as a pulmonologist/intensivist that consults, has clinic and occasionally attends in the ICU. Most academic intensivists will tell you that when they are on service, it is really busy. But when they are off service, they make their own schedule and do NOT have clinic and do NOT do consults. For those that also want to practice as a pulmonologist, they'll also have clinic and ward months as consult attendings. Consult blocks can run late into the evening occasionally. $
I hope to be an academic intensivist after a p/cc fellowship. Right now, I see myself more geared toward health policy research (resource allocation, leapfrog, regionalization, end of life issues, evidence based bundles, etc) and administrative duties (fellowship/resident education). On average, I'd probably like to attend in the MICU 2-4 months per year w/ 2 wk blocks at a time. I think this sort of diversity of responsibilities will keep me the most interested over the long run. Of course, academic docs don't get paid nearly as much as in the community, but when I'm not on service I'd be free to moonlight in Tele-units and stuff like that. If I attempt academics and fail or want to bail, I can always go out and get a community ICU job and get paid.