Legendary cafe Neon, famous haunt of Athens literati, fell victim to the crisis. But the cavernous space got a decent new tenant in Veneti (aka Beneth, if you read the Greek letters in English), which has filled the lower level with good-quality pastries, cookies, pies and even hot meals. There's seating upstairs and out on the square. Excellent service.
There are several other branches of Veneti around town, including one on Monastiraki.