state of art of freeradius

Hy all, I would like to know your opinion about the following issues: Which is the most common use of the freeradius server in your particular cases? Which version are you using? is it stable? What problems have you found using freeradius (during installation, configuration, use...)? My objective is writing a document trying to reflect the state of art of the freeradius server. Thanks a lot for you help Best regards from Madrid Rafa