It's not quite POO-roo. You can use the Mikropuhe speech synthesizer to compare puru and pyry. Puru is pronounced POO-roo and it means sawdust (among other things). The Finnish y is a close front rounded vowel (see here:
http://en.wikipedia.org/wiki/Close_front_rounded_vowel), like the German ü or French u. This vowel sound doesn't exist in English.