We loved the Intercontinental Athens. Upon entering, we felt like it was a true luxury hotel. The front desk was quick, friendly, and efficient. The concierge was very helpful and attentive.
The rooms were very nicely appointed. They were large, had very nice amenities, great bathrooms, very comfortable beds (you could choose your own pillow from a menu!), and were overall better than expected.
My only complaint about this hotel is the location. It is a little ways off (about 15 mins) from the center of the city (Syntagma square) and the Plaka district. The hotel operates a shuttle, but we didn't get a chance to use it. They told us that taxis cost about 3-4 euros. We got back pretty late from some of the tours we went on and wanted to eat dinner around the hotel, but we were surprised that there were very few options. The area is pretty dead at night.
On a side note, we booked tours through the hotel's official travel agency, Passepartout travel. DO NOT BOOK THROUGH THEM! They are a complete rip off and we had a lot of trouble with them. They completely overcharged us for airport transfers (charged us 150 euros when it should have cost 45), overcharged us for tours (at the price we paid, we should have gotten priviate luxury tours, but instead got tours with packed buses and double language). When we tried to get our money back, we had to really argue and fight with the managers in person (because communicating with them through email/phone was impossible after payment was made). So be careful!
Overall, I would recommend this hotel to a friend and would consider staying again, but I would also consider something closer to the center of the city.