I've been successfully using Pidgin since it was rebranded from Gaim and it has been integrated into messaging menu in Ubuntu.
But now in 12.04 after uninstalling Empathy and installing Pidgin, after successfully integration in messaing menu, Pidgin-libnotify is forced to be blacklisted and stops showin in menu.
How? After booting system I click on Pidgin in messaging menu. It launches, but after a while Pidgin dissapears from messaging menu and in ~/.config/indicators/messages/applications-blacklist/ a file pidgin-libnotify appears.
I've purged and installed again Pidgin and it still works as described above...