I haven't used it, but if you look up David Mendosa's website, You'll find a bit about it. He has lost so much weight, he's off all medication.
There's a Byetta thread on here somewhere.
you are very luck to be offered it especially if you are well controlled. In my PCT they won't give it to many people who need it, because it costs so much. they put them on insulin instead and compound their problems.