We also had HUGE problems with OwnCloud. It's a very heavyweight application and we ran into some of the same problems mentioned in one of the sibling posts. But probably the worst thing about OwnCloud is that we had files come up missing seemingly randomly. Unfortunately we were already several months into a site installation before we figured out what was happening. You're probably reading this and wondering why we couldn't just retrieve a copy from somewhere else, and the answer is that when OwnCloud eats your files, it syncs that state to all of the clients. This is incredibly insidious and as it turns out, this is an open secret among the OwnCloud developers and its community. Just Google for "OwnCloud file missing" and you'll get pages of results. You are really tempting fate if you use OwnCloud for anything non-trivial (which is probably the very reason you want it synced). It's like the dryer that eats your socks, except that it's your business documents.

What went wrong? And what did you end up using instead, and how did it handle the previous what went wrong better?

Can you go into more depth? Was it because of the number of users?