We have used VMware. We still use it; we didn't switch. OpenNebula is another way to offer cloud services.

I previously used OpenStack. I switched to OpenNebula because OpenStack has too many plugins. OpenStack is a lot of different products put together. The version control of OpenStack is very difficult to keep under control because when you put in a new plugin, something else breaks.

I have also used OpenStack, which is a much bigger beast than OpenNebula. OpenNebula gives you the ability to run simple VMs and containers, but it lacks many of the features available in OpenStack. It's great if you're only running VMs and providing developers with a way to automate them through the pipelines. In those cases, I would recommend OpenNebula because it is simple to do that. 

You should go with OpenStack if your use case is complex or you want to use templates. OpenStack addresses a much wider variety of use cases, but it is complex. OpenNebula focuses on one use case, but it is simple to use.

I tried to work with VMware vRA, which is very good, but because of its closed source, it's very difficult to add modules and customize it.

OpenStack is very complicated for the end-user so we did not use it because had we chosen it then we would have had to use many programmers and many infrastructure engineers. It is a very powerful solution, but I believe that it is only good for service provides rather than end-users.

 As it is now, we are almost done and our public cloud product is OpenNebula and the modules that I have mentioned. 

We previously used Proxmox, which cannot automate stuff.

We also used OpenStack, which is too hard to maintain.

I previously used VMware. From the management perspective, if you give both products to the administrators in the environment, OpenNebula is much more user-friendly and easy to manage than vCloud Director.

I can compare OpenNebula to OpenStack and VMware. OpenStack is also free, but it's too complicated to deploy into a production environment without specialized knowledge. It's okay for a testing environment but almost impossible to deploy in production. 

I haven't been involved with other cloud management tools. 

We previously used OpenStack. It's good for the services provider but not the cloud. OpenStack could be used for a data center. vRA is really good and better than OpenNebula but the license is really expensive.