Large clean just off the motorway to the airport. This is very convenient with a free shuttle bus to the airport every half hour. Rooms are medium sized, very clean and comfortable. Wifi costs and if you ask they will give an extra login for a second unit at no extra cost. We didn't have breakfast as the cost was rather steep € 17 each so we had something at the airport for a fraction of the cost.
Would I stay there again....yes as a convenient stop off for the airport this works well but only for that purpose. Not a long stay proposition.

Because I missed my connecting flight fron 7.45 pm to Heraklion - my fault: right time, wrong gate - my first inclination was to cross the street and book a room at the Sofitel. But a helpful Aegean employee advised me to get on the local shuttle bus to Athens for a fifteen minute ride to the nearby Holiday Inn, which would save me a lot of money. ( She could have told me about the hotel's free shuttle service, but she didn't, so I got on the bus.)

So I only stayed one (short) night at the Holiday Inn and there's really nothing to complain about: staff was very friendly, rooms are spatious and clean, breakfast tasted fine (specially for someone who never eats beakfast) and yes, at 6.30 the next morning the shuttle service was waiting outside the entrance and brought us in 10 minutes back to the airport.

I know where I'll stay the next time I miss a flight in Athens.

The hotel location is out of the Airport (10-15 min drive) if you take a taxi make sure you negotiate the price before, the shuttle time table is in the picture i have attached.
the hotel is nice, big and looks new. internet is good (9eur a day) and will allow only 1 device! how ever got a solution for that from the reception,
the room is big and clean, the TV is an old one and small.
breakfast is very good, big variety.
also there is a small Gym, the big issue with the Gym is that there is no water for drink, you need to get your own, never had this any other place.
there is a gas station by the hotel, you can buy there water and small things to eat.
nothing to do in the hotel area, is an industrial area, you have to take a taxi or bus to the city.

The Holiday Inn is the only place near Athens Airport apart from the on-site Sofitel which is quite a bit more expensive. Comfort was good, particularly the beds, but there were a couple of niggles. First, they charged 10 euros per day for internet access. This seems ridiculous, when practically every little taverna in the tiny Greek village where I live has free internet access. Then to top it off they wanted to charge another 6 euros for a 'second' device. We had a double room, occupied by myself and my husband. I wonder which of us they assumed had a computer? The room was also very hot and there was no way to turn the air conditioning below about 28 degrees - not exactly sleeping temperature. Would not recommend, except if you have to stay near the airport there isn't much choice at the moment.