We really like staying at Sonder when visiting the DU. It's a great location with many things in walking distance. The Sonder level is much quieter than a hotel as long as you don't book a unit on the busy street. The only issue we had is that the bathroom smelled very strongly of marijuana/cigarettes for at least half of our stay. Sonder addressed the issue and offered compensation for our trouble. We would stay with Sonder again although I would book a different unit. This is our 3rd stay at this location.
The only other issue I wish they would fix is the TV streaming. They use Chromecast which does not work well with Apple products. It can be done but it's tedious. If they would just have a standard smart TV with Netflix, Prime, etc then things would be much easier.