I discovered Wire several weeks ago and started using it (more as a replacement for Signal, while my go-to app is still Telegram). I was pretty impressed that the feature set was quite rich (compared to say, Signal, which is also end-to-end encryption by default), with multi-device sync, multi-OS support, photos, videos, sketches, voice messages, video calls, etc.
Wire is still behind Telegram in a few aspects, and I hope it'll become better soon. The main issues I see with Wire currently are:
1. No message delivered and message read indication. This is a big shortcoming for a chat application. Without an indication, it's almost like sending SMS and not knowing if the message reached.
2. The time taken for message delivery seems a lot longer than Telegram's. This in turn affects conversation speed negatively.
3. Finding other users, even those in one's address book (uploaded to Wire), needs a lot of improvement, and is currently buggy. Since Wire also allows signup using email address, it's important to allow users to be associated with multiple email addresses and using any of them for discovery and addition.
Additionally, it'd be nice for Wire to add the following:
1. Groups, super groups and channels for different use cases (all these terms are taken from Telegram).
2. Usernames to add people without exchanging phone numbers or email addresses. Along with this, @mentions to draw attention would be great.
3. If message editing is available, that'd be super cool, although I don't know about the complexity and limitations of such a feature in an E2E encrypted chat application. Telegram now allows editing messages for a limited time, and I no longer have to feel bad about typos, autocorrect, etc., and add more (annoying) messages in the conversation with corrections.
4. Easily mute conversations, for a short duration or permanently, from conversations or notifications.
5. Ephemeral (self-destructing) messages. I use this in Telegram's secret chats to exchange sensitive information that I don't want lingering around anywhere (of course, I trust the other party I'm talking to; so screenshots and related concerns don't arise).
I can't wait to move completely from Telegram to an E2E encrypted chat/call platform that's rich in features and works well. Wire is the only one I know of that fits the bill at this point in time, though it needs improvement. Having the code open source and independently audited by security experts would really help boost the confidence of users who value privacy.