I used the backend theme on a project of my own, I think it's perfect for the system you have, since there's some good examples on dashboards, etc.
Some usability gripes I have:
The width of the device management table should be a little more responsive, the horizontal scrollbar can be frustrating. Sometimes a double scrollbar (one under the other) is shown too which may be confusing to some users.
When attempting to connect to a device and the service is selected, the modal that presents the connection info has the 'disabled' attribute added to the 2 top input fields, preventing the text inside them from being selected.
Otherwise I think this is a great move forward for the project!
All the best