I've been looking at pain since coming to CRM 5 years ago. The one negative that keeps coming up is the patient population. Managing the "ups and downs" of these folks can be frustrating for some reps. This is one of those aspects of the job that probably doesn't really start to emerge until you've been doing it for a few years.
Again - this is all based on a conversations with about a dozen friends in pain and from what have gleaned off the boards here (which must always be taken with a grain of salt).
Good luck - I think that pain management will grow, so from that standpoint is probably not a bad place to be...
