The problem with Polish beer is not that it's hard to drink, but if you forget to drink water before bed, you end up feeling terribly hungover in the morning. This happened to me yesterday...after a litre of Tyskie :(
Lech Pils use to be regarded in high esteem in Poznań and generally in the whole Greater Poland, but the last few years saw a great decline in it's quality. The same thing happened to Żywiec, Warka, Tyskie... basically all the mainstream brews in PL.
Personally I stick to Piwo Noteckie and Fortuna Czarne, and not only because I'm a local patriot but because they are top notch, especially the later. Fortuna Czarne is heavenly, highly recomended, you can find it in your local Piotr i paweł market.