I volunteered in a BICU for a year a while back. I was not a nurse there, so keep that in mind with my answer
I did see a 1:1 ratio, but it was mostly the ideal situation rather than the norm. If your patient has a very large TBSA or is extra likely to need immediate intervention because of some other complication (major infection and the like), then you're more likely to get that 1:1 ratio. Otherwise, usually two patients, one more critical and one getting ready to step down in the forseeable future were assigned to one nurse. The pros and cons, to me, were pretty much the same as any other area of nursing that I've encountered so far. The hours are long and arduous, but the staff (to me) was more apt to work as a team and appreciate one another's hard work. Wound care is certainly not for the faint of heart, but it's something that you start to get used to. It can be more physically demanding than other areas of nursing, since during wound care in the tank rooms (and in patient rooms with a heater over the bed), it can be upwards of 85 degrees while you care for your patients (wearing full precautions, and that mask adds at least 10 degrees!) Burns were really fascinating to me though, since they are such a multi-system trauma for the body - if you like problem-solving and can operate well on your own, I think you'll really like it. Plus, the patients that I encountered were amazingly strong individuals - I think seeing positive outcomes in the BICU was even more wonderful than on other units, because usually you've developed a relationship with your patients and their families since they've usually been there such a long time.