I updated to the 1-19 nightly for the HD yesterday and was extremely happy to see that the local user profile image was restored to the "User switcher" tile in the notification drawer. I know it's just a GUI thing, but I really didn't like having my Google+ avatar in there. So thanks for that!
I just got my first spontaneous reboot ever (on any ROM) yesterday while granting superuser privileges to Battery Doctor to prevent autostart for some apps. But I haven't had any since. Also, on one of the nightlies a few days ago, wi-fi once reconnected after sleep to a neighbor's network, instead of mine. But that hasn't been repeated since then. Other than those 2 minor things, performance with CM 11 has been rock solid and stable.
There is one thing -- Battery drain seems to be slightly higher with CM 11 than on stock, but only while in actual use. While sleeping, it's actually a little better, getting 0-1% battery drain overnight.