Very quiet on a Sunday!
We came here on a Sunday night to find it very quiet and only a few of the floors were open. It's 180 CZK (£6 / €7) to get in, but the drinks prices were quite reasonable. The draught beer was 45 CZK (£1.50 / €1.75) and service was friendly. I didn't see anyone order anything else other than beer, but there was quite a lot of people who were just drinking soft drinks.
We arrived about 10:30pm and were the first ones there ... it did get a little busier and certainly the 'dance' themed floor filled up, but it was still very quiet.
Some of the music didn't really fit with the 'theme' of the floor, and was a little random at times.
That aside, it was good fun and would recommend if you're in Prague.