Have two such UPSs in use. The average load on both is about 25% and the tests with interruption were all successful.
Update Dec 2019:
After 4 years, the first battery is now through its life. For this price range of UPS absolutely ok and convincing! It has kept my servers clean and shut down in a controlled manner more than once.
Pro
1U -> space-saving
Rack mount is included
Runs without problems via USB to NUT on a Raspberry2 as server for the status
Has proven itself over the years and runs reliably
Contra
The safety device to prevent the plug from falling out is suboptimal
The supply line to the UPS does not have a fuse to prevent it from falling out.