Here are my gripes.
- Pages load pretty slow over mobile networks. Every app page requires like 5 seconds to load, as it loads the page in 2 steps, first the page and then then the content. Not talking about navigating folders in Files but apps like Calendar and News are especially slow.
- Bookmarks app silently stopped working few weeks ago when I thought I kept adding Bookmarks through Android mobile app, so I lost 2 weeks worth of them. Not sure if the server or the client app went wrong but I switched to Pocket even though I run everything self hosted where I can.
- Contacts app previously had a problem where you couldn't save more than one information per page reload until recently when used through CloudFlare which was very confusing to see some saved data disappear.
- News app's UI is a bit of a joke in terms of speed and usability, so you need a mobile app to consume it than from the web.
- Frankly all of the apps need mobile apps because pages load slow and it's reluctant to go through them from the web but the mobile app quality varies so much as they're all dependant on third party developers.
- NextCloud talk, I had a high expectation of it but no matter how I tried, it never worked reliably and client apps were nowhere near the quality to recommend to non tech work people.
- Using an external storage for Files makes the performance and reliability quite low and when you think about using it for work, you need maximum reliability but I ended up using local storage as that seems the only way that's tested enough.
- You can't tell how much of a file is uploaded reliably at all. The "seconds remaining" display jumps all over every second as it's probably calculating from the speed of the moment instead of averages of the last minute or something and you can't cancel the individual files queue.
- I have basic auth on the NextCloud instance but the official NextCloud app refuses to work through it, even though the web version allows you to have yourself logged in via basic auth.
- Email app acted like an alpha version, so I instead use integrated RainLoop which is fine but I couldn't get people to login automatically using the NextCloud logged in user even though I have that option turned on, instead I had to edit some source code to make it happen.
- Logging out takes forever.
I am impressed that the look and feel is good and the caldav being so easy to use but I'd say it's close when it comes to overall quality to have work people use it than just for yourself.