I have been using A360 Collaboration for Revit (C4R for short - that is what they call it on the AutoDesk forums) for over a year now on multiple projects. It works great and seamlessly. I have only had one instance where I lost work and that was when another user's computer crashed while he was in the model and it corrupted the model in the cloud. We were able to restore from a previous version and only lost about 2 hours of work.
The administrative process to get the project setup and invite users is a bit cumbersome, but once you get past that hurtle, things are fairly straightforward.
In my opinion, this is an invaluable tool to allow small firms (and big firms alike) to collaborate with each other. Give it a try, you will not be disappointed.
Feel free to send me a message directly if you have more specific questions.
Regards,
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Philip Bolender AIA
Principal/Owner
Bolender Designs, LLC
De Pere WI