Arno was a terrific host. And the apartment was great. Kreuzberg is a great neighborhood-- hip, food-filled, convenient. We didn't see Arno after check in, but he was very helpful. Since we had a late flight, he was flexible with the check out. Only a slight communication problem with the Berlin tourist tax--things just got lost in translation on both ends.
Just Be forewarned that you will have to pay 5% tourist tax before you leave.
Despite that slight snafu (no big deal), Arno is highly recommended as a host!