It's easy for me, a few years post divorce to encourage you to let this go. However, when I was freshly divorced, I can remember going through similar thoughts, feelings. I took my maiden name back - I didn't want to be among the string of Mrs. whathisnames (he's on #3 now). I took his name as a symbol of our joining our lives, when that was done I felt the only appropriate thing to do was give it back.
I can understand women who have children maintaining the same last name as their kids. Other than that, I don't get it.
Yes, it's a hassle to change your name. So is a divorce. It's all a part of the package.
Feel what you feel, talk about it, sometimes yell about it. Then keep walking forward as you so admirably have. You're doing better than I did, believe me.