It takes a little while to get the right balance of collection cup height and the overflow box height. But once it kicks in it works great.
I've had mine for almost a year.
The pump will run dry due to evaporation, so I top off the tank a little bit every day before going to work.
I hope you bought the version with the overflow tube pre-drilled in the collection cup. If you have the collection cup too low the muck will be wet. Mine pulled out about a gallon (US) in a day when it was too low. If I didn't have the collection cup with the overflow tube it would have been a huge mess. The overflow box prevented more from being pulled out of the tank, since it started to run dry. Once I got it set to the right height and topped off daily it works great!