Just finished the Athens part of our trip. Took one awesome tour and another horrible tour. Here's the scoop:
Athens walking tour - EXCELLENT!! The guide was amazing, the tour was so awesome and it gave us such a great picture of the city we were able to navigate the rest of our time in Athens just based on this tour. Highly recommend. Here's the website (we took tour #1):
Athens by Night - hopin tours - DON'T BOTHER. It was awful. The driver didn't pick us up at our hotel (Hilton) as promised. He didn't explain anything about what we were driving by and seeing. Then he dropped us at the restaurant and left us there w/ no explanation of anything. The dinner was mediocre. This tour (at 58 euros) was way overpriced and just not worth it.