Gorgeous place, not only for holidays, but also for work! I spent a month here to work remotely and it was just perfect - super fast internet and everything you could need is just around the corner. I got provided a small handmade booklet with all the restaurants, coffee places, late-night shops and directions which was definitely a big plus: this way you get to know the good places, which the locals recommend and don't end up in your typical tourist trap. Needless to say it was tidy and clean, and whether you work inside or on the green terrace is up to you :D
P.S: Although its in the center of Athens, it was so calm at night, because its located in a small pedestrian zone where no cars are allowed.