I can't say that it hurt me at all to see my ex with someone else. I didn't mind being replaced because I had spent years in Al-Anon before I left, and I think that mentally and emotionally, I had checked out if my marriage long before I physically left.
For me, the best times post-divorce has been the periods AXH has been dating - because then he has left me alone. He needs someone to control and manipulate and I'm very glad when he focuses that on someone other than me.
I think it's sort of like... You have a fancy car. You can't make the payments and it gets repo'd. You still need a car so you buy a beater from that guy with the alley garage. That's what your ex is doing.