Well, been to NYC couple of times, not impressed by the clubs, i prefer clubbing in Berlin (espectacular), shanghai, Paris or Sydney, had the best time ever!!
Warsaw i heard has pretty good clubs, but if you are after that "i want to be seen, or i want to feel like VIP, then you should definately go back to the US, we in europe have already grown that up long ago.
ftb.pl is a good resource for clubbing culture in Poland, there are alot of good clubs/parties/events everywhere in Poland with world class DJs like PVD, Oakenfold, Tiesto, Richie Hawtin, etc etc
im a promoter/dj in canada as well and going there this summer hoping to do a little mini DJ tour at some clubs if i have the time..