This is definitely a budget hotel. Nearly a hostel. Great location and price, but you do get what you pay for.
We spent 1 night in athens and only a few hours in the actually hotel. The rooms are dated and run down. Our room smelled of smoke and the bathroom although looked like it was just cleaned , wasn't somewhere I would shower without my slippers.
The staff was very nice, we missed breakfast on check in and check out so I can't comment on that.
When trying to find the hotel, do not used the map on their website, it's not really adequate.... google map it.

The location was ideal and made it easy to see all the sights in a day.

I only recommend this hotel for a short stay but if your planning spend some time in athens then maybe look elswhere

Excellent location near tourist sites. Breakfast is included in room rate: juice, tea, coffee, lots of bread, pound cake, jam and a hard boiled egg per person. They sold bottled water in the lobby.

As our flight into Athens was canceled, we called Nefeli to change our check in date and was grateful when they obliged.

Unfortunately, we were given possibly the worst room in Nefeli. If I remember correctly, it was room 102. There were 3 single beds in there with no TV. One bed had no sheets and looked very dirty and old. The floor had a layer of dust like it hadn't been cleaned for months...My spouse couldn't sleep at night and had difficulty breathing, possibly from dust allergy.

Staff weren't very friendly and reluctant to share information. We wanted to watch the world cup in the hotel lobby but the staff told us that the broadcasting crew was on strike so they didn't broadcast world cup that day, and he continued watching news in the lobby. So we went out and found a cafe only a few blocks away with world cup on their local network!

Definitely our least favorite stay in Greece, thank goodness it was only for 1 night.

The hotel is conveniently located in Plaka, is basic but clean. The breakfasts are also basis but adequate. We found the staff very cool and unfriendly.

Small hotel, rooms a bit dated but spotlessly clean and with comfy (if a bit squeaky!) beds. Helpful staff and an adequate breakfast of orange juice, tea, coffee, bread, eggs, toast, cheese, jams and cake. Nearest bus and metro station is Syntagma Square - the central square where the Parliament Building is. Take bus 95X from airport - it leaves from just outside arrivals every 15mins and takes approx 1 hr to Syntagma Square. Nefeli is minutes away from Plaka - the old part of Athens at the foot of the Acropolis. We could see the Acropolis reflected in the window of the building opposite. Plaka is great at night - loads of tavernas and a lovely atmosphere. Everything is within walking distance of the hotel - it took us 40 mins to walk to Lycabettus Hill, 15 mins uphill to Acropolis. The metro is clean, modern and feels safe but, as in all cities, watch your handbag and wallet. The location of this hotel is superb and in a really safe part of the city. We couldn't have chosen better for location and value for money.