I was in Poland last spring, and I had a fantastic time.
Didn't spend a lot of time in Warsaw, but spent a day in the old town square. Lots to see there, the castle, some cool churches etc.
If you get a chance, I'd swing by Krakow. I spent a lot more time there and had a great time, there is a lot to see. If you can, you must head to the salt mine at wieliczka (which is near Krakow):
http://en.wikipedia.org/wiki/Wieliczka_Salt_Mine
One of the coolest places I've ever seen.
Edit: Damn, beaten to it by Makarov
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