I think it very much depends on the situation. My husband was married twice before me, and was with each for a number of years -- two biological kids and one step with the first wife, one kid with the second. I met him 10 years after he and his second wife mutually agreed to end the marriage, and we married a year and a half after that...overall, about 12 years since his divorce.
In the case of my own husband, yes, he DOES still have feelings for his second wife. That said, they're not the same feelings that they were while they were married. It was an amiable end to the marriage, and they've always been on friendly terms. While I'm glad they don't correspond, I also acknowledge that he still likes and admires her personality. This fact did bother me early in our relationship -- I felt like I had to compete, and constantly worried that there were still romantic feelings there. Over time, my worries have been put to rest. I've gotten to know her a bit, and their son a bit more, and of course gotten to know my husband much better. I'm convinced that the feelings that should be given to a wife are exclusively mine, but that doesn't mean that she means absolutely nothing to him now.
On the same token -- he married first wife when he was fairly young, and it quickly morphed into a nightmare with someone he really did NOT know. They divorced after he discovered her infidelity, and were on very bad terms for a long time. Now that the kids they had together are grown, he has the luxury of never even having to think about her.
So...yes, it's an individual thing. He may or may not still have feelings, and that may or may not be a bad thing for current or future relationships.