I'd easily recommend ownCloud to small businesses or teams within organizations. I've not used ownCloud in large deployments, so I'd hesitate before suggesting it in a situation where more than 10 users need support. That said, ownCloud is easy to set up and multiple instances could be used to service a large user base.
Attention and dedication to making the product a world class product with continual product updates.
Ease of use from an administration standpoint, and a very Clear UI.
The price -- you can't beat free!
Mobile applications are great.
Integration with public S3 cloud providers like AWS S3 and Wasabi S3.
2FA authentication is supported and works great!
Marketplace Add-Ons: I love this! For example, I can install an add-on that natively opens raw images. I am a photographer as well, and being able to quickly view the CR2 Raw Files direct from the camera is fantastic! This was made possible by a marketplace add-in.
Embedded Media Players: Photos, Music, and Video files can be viewed and played right in the browser window.
Sync application to keep local files on a computer updated with the files on the server.
Access control and permissions -- shareable links!
Some access settings are mutually exclusive for performance (REST vs. CIFS)
QoS by Tenant requires use of external ADC (Hitachi suggested and sold us Pulse Secure) and their support on this product offering is not up to their normally high standard
Inability to easily collaboratively edit the same document by several people. Some advances have been made with Collabora (Libreoffice online) but it is still very sub-par compared to Office365 and desktop/online Office editing Sharepoint or OneDrive documents.
Apps for Calendar and Contacts are not part of the basic core, and although now quite supported they cannot still be easily deployed in common email clients such as Outlook or Thunderbird, separate CalDAV and CardDAV plugins need to be installed. Embedding an email solution and plugins for major email clients so they can work just by entering username and password would be good.
Risk of moving important folders/files to another location just by random drag-and-drop on Windows. Sometimes this breaks public links that cannot be restored anymore. Reverting such mistake by any of the users is impossible automatically.
When some user deletes some data in a shared folder it is put into recycle bin of the owner of the folder. The user who deleted cannot himself/herself revert such action as he/she does not see the recycle bin (trash) of the owner. Also, there is no log in the recycle bin who deleted that file or folder.
OwnCloud is easy for me to use, and I believe it would be for others too. The barrier for most people will be the set up. For a technology professional like myself, ownCloud's setup is pretty straightforward, but it's not the sort of thing most casual users will be able to handle. Also, it's on the user to maintain the service. These can be taken care of by paying someone to do it for you.
Compared with other cloud services, ownCloud has been the most efficient. It doesn't create a noticeable drain on resources and very quickly syncs across all my devices. I'm usually able to save a file on my laptop and by the time I walk over and sit down at my desktop machine, it's already there. I don't need to wait as often as I have with services like OneDrive.
Regarding the community edition, there is a reasonably good support on the IRC, forums and in the issue section on Github. Perhaps a much more individual approach would be available if the premium support was chosen and the instance of the server was provided by the Owncloud company that also offers some premium extensions, not available generally. However, we did not need this level of support yet.
The paid cloud services are expensive if you need a lot of data. You're giving your personal and business information to a data-hungry organization. Local NAS solutions are too slow. We run ownCloud on an older business PC and the performance is outstanding, even for remote access, due to local syncing.
