My friend and I stayed in Siddik and Tax's apartment for two nights and were very happy overall. To begin, the location couldn't really be better for a tourist. The neighborhood felt very safe and was within walking distance of many restaurants, bars, and tourist spots. It took us about 15 minutes to walk to the Acropolis.
The apartment itself was really clean, the wireless internet was very fast, and was really comfortable for two people. When we got there, Tax sat down with us and gave us a bunch of tips on where to go, how to get there, etc. Tax also provided bottled water for us in the fridge (although you can drink the water from the tap) which was really nice.
Overall, an excellent apartment to stay in while in Athens. I would definitely stay in the apartment again.