RoundCube 0.2 Beta has been released. Based on that verion, i've created a new version for ISPConfig 2 today.
Although it's Beta, it contains many bugfixes and improvements.
During testing, i was able to login with username AND email@example.com
Also the identity problem seems to be better as well.
user@localhost will change automaticly into firstname.lastname@example.org
For more information have a look here