There was a lot we liked about our first Sonder stay. Check-in was very easy. The quality of the accommodation was very high - hotel quality rooms with all the benefits of the kitchen, lounge etc. The communal areas were kept very well. The air-conditioning was excellent and the wifi worked well. There were a couple of small issues though -
1. Location - it's quite far from the centre of Washington and the more lively Northern and Western areas. The circulator bus is good value at $1 and goes nearby but stops quite early at night. It's a good 30mins on foot to the Capitol. Ubers do work but factor them into your planning/costs as you'll need them.
2. Noise - they leave a "white-noise" machine (which doesn't really help) for a reason. We had a lot of noise from kids staying upstairs (felt like they were going to collapse the ceiling!) and from outside - traffic and dogs barking at a neighbouring dog school. Bring some good ear-plugs!
Overall we liked the place but I don't think would stay again for those reasons, but would certainly try Sonder again as the property standard was very high.