After reading the transcript, I am of the same opinion. The only area that I see as a possible success in the appeal is whether the trial judge improperly excluded the testimony regarding the 2nd "drug smuggling incident" I may have missed something, but it looks like the factual sufficiency grounds are out and I don't see anything else in the pre-trial or trial transcripts to show much hope on the appeal. There are some sealed documents, so they may yield something. At this point I give the appeal a 10% chance of success.
What about the issue of not giving Davila complete testimonial immunity? Mary Stillinger argued to the judge that the immunity he did have would not protect him if he admitted he was carrying a gun--as well as for other drug related activities. She argued that the not immunizing him for other drug activities permitted the prosecution to unfairly characterize him as a naif about the drug trade.