Signal is awesome, which is why we want to use it, but then suddenly the user finds they're now inextricably tied to Google or Facebook collecting their metadata - while we know Google themselves have been compromised (technically & legally) and are forced to hand that data over. Notably, to an NSA that has lied to Congress about it's operations, without consequence, and hence is now beyond oversight and reach of regulators too.
Also that the iOS code, which appeared to be free & open, is actually not, because other projects are denied permission to use in a way that's compatible with iOS's App Store). Ironically because the libraries are under GPL. Hey, blame Apple I know, or ourselves for not reading all Apple's T&Cs before promoting Signal, but it's disappointing none-the-less (while also still being OWS's right).
From all their history, the OWS guys seem to really want and be trying to do the right things, within the constraints and trade-offs available to them. The answers aren't trivial, but something about where it's all ended up leaves a very uncomfortable feeling.