@nextcloud My favorite feature is how lightweight the sync client is. I use a very CPU-intensive backup app - now I run it on my NextCloud server instead of my laptop.
Least favorite feature is that the web-based upgrade doesn't check for incompatible plugins. Spent an afternoon diagnosing errors after upgrading - because 1 app wasn't compatible.
Most important missing feature: federated talk. I want to chat with my other nextcloud-enabled friends without using guest links.