The flat is amazing, but there is one thing I wish I'd known before booking: it overlooks a beautiful park, but the rosegarden features an open-air bar with DJs and music about 50 meters away. It is a really nice venue - for many people, this would be a huge draw! However, music is clearly audible on the balcony and in the living room all afternoon and evening (and several times over the long holiday weekend, people were playing loud music in the park until well after midnight!)
To be fair, the bedroom is at the back, and the soundproofing is excellent - with the windows closed, you can sleep fairly peacefully. But in the summer, you really want to have the windows open and enjoy the balcony and fresh air!
The flat is beautiful and spacious, it had everything we needed. You cannot beat the location, and the neighbourhood is fantastic - but just be aware that central Berlin parks are *extremely* noisy during the summer.