Besides my regular work,
I am working on upgrading a 12.0.6 instance to 12.1.1.
Though it was not mandatory to upgrade database, I have upgraded Apps 10.2.0.3 Database to 22.214.171.124 with some issues to work on.
Still to be done as part of it are:
10.1.2 HOme Upgrade
10.1.3 Home upgrade
and finally the maintenance pack of 12.1.1
Will do it and come up with a post on upgradation ,most probably by this weekend.