I've been installing various ROMs (CM11, SlimKat, AOKP etc..) on Mega and been testing them out.
This is my review / guide / tip / bug report for those who want to check them before installing on their phone.
Please note that there are more than one versions available on each ROM, so experience maybe different on each versions; new features maybe introduced hence new bug can be found (or removed)
Developers are constantly releasing new updates so please check XDA site often. Please visit XDA Galaxy Mega site and check ROM thread (especially Silesh.Nair's posts)