Micro is most often performed by hand surgeons. 3 routes to hand. General, ortho, or plastics with 1 year of hand/micro fellowship. Ortho and plastics usually get good hand training in residency. Plastics usually gets good micro training in residency doing replants/free flaps and the like. Ortho doesn't really do micro in residency.
Plastics residency is probably one of the most competitive right now. Something like 250-275 applicants for ~75 spots this year. Ortho is competitive, but not as bad. GenSurg is becoming more competitive, but is still pretty wide open.
Hand/micro surgeons do fairly well in private practice, but I couldn't quote any reliable numbers. Let's just say that you won't have to eat at McDonald's all the time.
Hand surgery is super-fun and you get to sit down (very nice). Micro can be tedious sometimes.