The apartment is in a great location in East Berlin, and so it is really near all the major sites. Three of us stayed, and we found the apartment had plenty of room. The supermarket across the road is so handy, as is the Underground station literally a minute's walk away.
Michael is a really friendly guy, and met us at the apartment, and showed us everything we needed to know, as well as leaving some literature and plenty of tips for things to do in Berlin. He also said we could contact him at any time if we needed to, which was nice to know.
Thanks Michael!