Like I said in the recent Amsterdam hotels thread, I just got back from there and it's now my favorite city in the world. The whole atmosphere and feeling I got while I was there made me feel very comfortable and right at home. I'm half dutch and I understand some of the dutch language so that helped.
If you like music, there's a bunch of cool record shops that offer an incredible selection of CDs/LPs that are often hard to come by in NA.
I never got busy with any whores, but I did spend alot of time in the Red Light District just taking in the "sites". Visit this area past 11PM while drunk for an even cooler experience.
I also went to Paris while in Europe and it was incredible as well. A completely different atmosphere and feeling then Amsterdam, but still awesome. I consider the metro system in Paris to be the 8th world wonder.