Athens - Omonia Square

The area is basically fine and, as someone else has said, Athens is still a very safe city.

I think, if you don't know the area /Athens Omonia can feel slightly intimidating, especially at night as you have quite a lot of big groups of men hanging around on the street. I'd stress though that these are 'groups' not gangs. Essentially a lot of immigrants have come into the area in the last 5 years, there's little in the way of parks in that area, and the square is a social venue to meet, chat and smoke.

We walk through Omonia until quite late at night and have never had a problem. As with any big city it is wise to be aware of your valuables when in crowds, but I've no reason to assume pickpocketing is any more prevalent in Omonia than elsewhere. Two friends who stayed in Kolonaki, the rich area, had purses snatched.

On the up side you are only a few minutes walk from the bottom of the Acropolis, and the teeming market streets between the hotel and there are a site in themselves.
Alan

Athens is a safe city, I can't tell you about a particular suburb. AS far as I know Omonia sq. is a very popular turist place with many budget hotels.
Try to ask the question on tripadvisor also.

It's fine--I wouldn't get stressed out about it but would watch your pockets. It's notorious for pickpockets (although I've never had any problems).