Both of my girls have been great nursers (one is five months so still nursing), and not so good with the bottle. We have tried a ton of the recommended bottles-Avent, Tommy Tippee Closer to Nature, Dr. Browns, Nuk, etc. After much drama, the bottle that both of them have ended up taking is a Nuk bottle with the orthodontic nipple. However, neither of them have ever really gone back and forth easily. They both strongly preferred to nurse, and would basically just take enough to get by until I returned. I stay at home, though, so if you are going back to work and they consistently have to take a bottle, maybe it will be better.
I did childcare for a baby a couple years ago who also had this issue. The nipple that ended up working for her to get used to a bottle was a cheapy disposable, the kind they hand out at hospitals.
http://www.drugstore.com/products/prod.asp?pid=355177&...
I think for her it helped that it was small and didn't gag her.
Every baby is different, so you'll have to try out some different bottles to see what works.
Good luck and best wishes!
ETA: oops, I don't know if the link I put in worked. Anyway, the nipple is the disposable enfamil slow flow soft nipple.