Quite a few bugs were fixed, (camera!), a few apps (Play and Gmail) were updated as well.
I don't have an exact list because Mrg666 builds me sort of a hybrid, mostly pure IHO, with a few tweaks, and then I work from there. I could look at changelogs, but I really hate doing that, lol.
If things are working and you are happy with what you have, then there isn't a pressing reason to update really, but I suspect you will probably have some things fixed. What you could do is do a nandroid backup and give it a try, if it doesn't improve, just restore your backup.
Take a look at my backup and restore guide, you can do a complete changeover in 10-20 minutes.