Favorite solution for user management and billing

Hi guys,
I would like to know what is your favorite Customer management solution? I’m currently using User Manager, but it’s pretty basic, and I would like to migrate to a “more powerful” solution. I’ve been considering Mikrobill, any suggestion?
Do anyone know a platform able to offer different limits for international and national bandwidth? I’ve one BGP capable connection just for national and another for international bandwidth.

Thanks,

I use Radius Manager , quite cheap and works pretty good with tons of features.

Live demo here.
http://radmandemo.dmasoftlab.com/admin.php

http://ibs.sourceforge.net/
also a commercial version of ibs is available at http://parspooyesh.com/