I haven't really had any issues per se, at height about a year ago I had just over a dozen contacts on signal. The biggest UX deal breaker was no profile pictures. You can set one, but almost no one will ever see it since almost everyone uses Gmail or another cloudy email provider that will sync or store ancient Google+ (or equivalent) avatars to your contacts. Signal chooses to display a contact photo from your device over what a user sets. This is insanely counterintuitive approach and no other app works that way, meaning no one expects it to work that way. My family and all but two contacts moved back to WhatsApp. I'm glad to read they're focusing on UX now, but I can't bring up switching again with these people. Maybe when or if phone numbers are abandoned, then I won't have to link/associate contacts to my address book and see those old avatars.
Multiple companies I've worked at have been in the position of their competitors suffering security breaches. In all instances there were communications sent to all staff not to speak externally pointing to the inident for publicity/promotion of our service. While you can't turn a blind eye, it's just not a good look. Besides, tomorrow it could always be you/your company.
Telegram has some positives, but the lack of e2e without secret chats is inexcusable--notnto mention secret chats' notifications are crippled (no option to see sender or message content.) If only Signal had working profile avatars instead of seeing some ancient Google+/Facebook/social media photo that sync'd to their contact list eons ago they didn't even know was there... Small UX things can make all the difference, haha.
No such luck on Android, you need to use tasker or similar. Really a nuisance but not a deal breaker. It would be dreamy to set up the client to not use specific SSIDs.