Need Asterisk Reference

Good afternoon,
I work for a company that provides an Asterisk solution to local companies based here in Austin, TX. We are just at the beginning stages of this thing and one of my prospects has asked if we know of anyone else either in Austin or generally in Texas that has been using Asterisk for a while (6 months or longer), that would be able to provide some evidence of a good experience with Asterisk before they commit.

Would any of you be able to provide a reference as to the system in a short phone call?