I also wish I had not changed my last name. This was the only thing we fought about before the wedding. My husband felt really strongly about it, so I changed it. Of course, a couple of years later, after rethinking many of his "ideas," he told me he really didn't think it was a big deal and I could change it back. I didn't want to go through the trouble. I also use my birth name as my middle name, which is extremely common around here. I don't use a hyphen, but on anything official, I sign both last names. Both of my boys have my last name as their middle name. They hated it until we moved to an area when at least 50% of the kids had hyphenated last names or at least their mom's name as a middle name. Now, my older son will sign his full name on documents, while #2 uses an initial or nothing. In fact, he still doesn't spell my name (his middle name) correctly half the time. He just feels it's too long to write.
I'd say at least half of the women around where I live keep their own name, and probably closer to 80% of the younger women.