But "ZEZWOLENIE NA POBYT REZYDENTA D£UGOTERMINOWEGO WE" (permanent residency) doesn't give any extra privileges in Poland which EU country passport wouldn't already give.
It does give one important privilege - you can't be deported then. EU citizens can still be legally deported after 3 months if they don't have a reason to be here - the same law that the French used against the Roma a while ago. It's also very useful in turbulent times - for instance, a couple of years ago, there was some very real speculation about countries leaving the EU, and it is a gateway to citizenship. In my case - it will be very useful if Scotland votes yes to independence, as it'll be a guarantee of residency even if Scotland ends up outside the EU.
In Poland we have "meldunek" - registration of living in specified apartment. Poland is in Schengen, so somebody from let's say Germany could do "meldunek" go back to Germany and nobody would stamp his Visa, register that he left the country. After 5 years he could claim that he was for whole time there in Poland.
Doesn't work like that, unless it's on the basis of marriage. Those applying for permanent residency on the basis of work need to have a verifiable work history for the entire 5 years - and they will check.
As for Polish citizenship - passing a State exam in Polish is now required.