- message delivery was not very reliable when your connection is poor and intermittent (think wifi in the underground between stations)
- when you need to resend a message in a group, you need to tap "retry" once for every recipient in the group
Issues that my friends complained about, justifying their non-use of Signal:
- you cannot create links to allow people to join groups (obviously this is a nonstarter, without first allowing people to be in groups pseudonymously)