The Cypria is very much what everyone else says it is, in these reviews: a moderately priced, very convenient and decently appointed hotel. By USA standards it would be classified as a 3 STAR hotel, however by Greece/European standards it definitely deserves its 4 STAR rating.
I suggest getting to the hotel by metro, rather than taking a taxi from the airport. The metro is 5E/person (one way) from the airport, vs the 35E or so taxi fare. It takes about 40 minutes by metro, 25-30 by taxi. With our conversion rate being rather deplorable, and since you're looking at THIS hotel I know you're into saving money. The metro leaves every 30 mins, so plan accordingly(bathroom breakes, etc), so you dont JUST miss it and have to wait another half an hour.
It is the only metro line that comes to airport. It is designated as the BLUE line, but I never saw how they figure it's the blue line. Do not confuse the metro with the urban train at the airport, however, you may not get where you want :). The metro has an M on it. Duh! Trust me, though, when you get there you'll be happy you printed this out, it can be rather chaotic.
Your station is Synthagma, which is either 11 or 12 stations from the Airport.
Once you get off the metro, follow the exit signs and the street right in front of you is Ermou(it has a McDonalds at the right corner). Go down Ermou(about 200-300 yards) and you will eventually see a Bertolucci store sign. That's where you turn right and the hotel will be at the end of that small side street, about 30yds or so on the left.
I am writing this because it can be very confusing and a fellow reviewer has paved the way for us to make it there in a reasonable time, without getting lost.
The hotel itself is basic, but clean and decently comfortable. The AC works fine. It is a wall/window unit but it is very quiet and it's remote control operated. The breakfast is basic:omelette, cheese, juice, coffee, but it definitely does the job.
The Plaka is really cool, although we didnt do a ton of actual shopping. Mainly trinkets and such. Do not buy pyrated DVDs, the quality is REALLY bad.
I really recommend the Eggplant salad at the Hermion restaurant, as well as the Nutella/Ice Cream Crepe for desert.
There is also an amazing art gallery in the Plaka, called Athens Art Gallery, which I highly recommend if you're in the market for original paintings that are super reasonable and can be shipped to your doorstep with insurance and frame, within two weeks. Needless to say we made an unscheduled purchase :). The artist is a serbian refugee, in his 70s, that occasionaly is in the shop and is one of most charismatic/interesting people you'll ever meet.
Athens itself is an interesting city. They have cleaned it up considerably since the Olympics, but it still has a dusty, old and ran down feel to it. I really see no reason to spend more than two full days in it. The Acropolis is a MUST, but the Archaeological Museum left me rather unimpressed. Make sure you have plenty of water with when you visit the Acropolis, especially during the hot months, as there really isnt anywhere to get water once you're up there.