I spent a week here in August and it was very nice. It's on the ground floor facing the street so easy access, with huge south-facing windows onto the park. There are no nightspots on the street so it's pretty quiet after dark despite the sidewalk-adjacent location; also there is a metal gate which rolls over the windows and essentially blacks out the space for sleeping. That said, there are lots of great bars and restaurants a short walk away, including a nice coffee spot right down the block although it doesn't open till 9.
Wifi worked great. Hot water was HOT and plentiful. Lots of towels and supplies. The metro station is just a few minutes' walk. Plenty of sketchy activity around the station and park, namely drug dealers, but no one is menacing; if you're not looking for drugs just ignore them and they will do the same. The neighborhood is also full of young families pushing strollers; it's a vibrant community with people of every type and nationality, doing everything you might imagine--no one cares or bothers anyone, that's what makes Berlin great.