You'll get more responses over in the CC forum and maybe one of the moderators can move this But in short, the PCCM track is both to make you more marketable (many groups/hospitals want someone who can also cover pulm consults at the least, +/- pulm clinic since it is possible to get a job where you do only ICU/pulm consults) and for some people, to give you something to fall back on. It will also make it easier for you to find an academic job if you want one as most academic jobs will require you to do clinic in your other specialty, whether that's pulm/nephrology/ID/cards. The anesthesia/ED people also often cover the ORs/ED in academics, less so in private practice.
I'm IM->CC only (starting fellowship next year) and so I'll let the combined people otherwise chime in, but I think part of the burn out has to do with what your interests are when you start. There's lots of PCCM people whose primary interest isn't the ICU and who lean more towards the pulm side. I would say it's important to have a sense of what you find rewarding/stressful. For me, I've learned that a full day of clinic leaves me about as exhausted as a month of Q3 28 hour call in the MICU, so the combined track wasn't the right path for me. I recognize I am in the minority there. I also know that by taking the IM->CC only track I am limiting my job prospects compared to those who do PCCM or some other combo.
Hope that helps.
