I haven't worked Poison Control since becoming an RN, but did work there as a nursing student. I took calls just as the RN did, but worked under their supervision. It was an interesting job, but not much room for advancement for the nurse that I could see. We sat and answered phone calls. There was a nursing supervisor, so I suppose there was that option for advancement. It could get incredibly tedious. On rare occasions some member of the public would show up with a creepy crawling critter for us to identify (no thanks, I'm not a wildlife specialist) to break the monotony. But tedium can be nice sometimes. I think it would be the perfect job for someone who couldn't handle the physical demands of bedside nursing. It's a 24 hour place, just like the hospital, so there was the potential for night shift.
The nurses did seem to like it. I don't know about their training. They had a computer program they used to simplify the job. Type in the product consumed and up popped all the information you needed. Very straightforward.