Update: the nightlife pass actually didn't work out. The company hasn't brought it to my hotel as they had confirmed with Isango. They didn't respond or could be reached . Isango refunded me the payment without any problems fortunately though. The pass wouldn't have been necessary at any rate though - seems to me that it is better to look for the in-Clubs and places directly when you're there. -- When the stores are closed, the park is dark and you don't want to spend "a night at the museum", what do you do "from dusk til dawn" in the city that never sleeps? Hit the clubs and get dancing!
That's where I found the "Nightlife Pass New York" via isango. It offers direct access to about ten big clubs in Manhattan, most with a welcome drink and some other perks; 7 days are about 90 Euro. I guess that's a deal, and I'll find out!