I have cycled almost the entire R1 through Poland. The whole R1 connects Calais in France with St. Petersburg in Russia. I chose an existing long distance bike trail because usually these routes are great for sightseeing, go through interesting landscape and most importantly avoid dangerous road sections. I say "usually" because unfortunately the R1 has been a disappointment in all three aspects.
I have not made a single longer sightseeing stop - basically because there has been not much to sightsee... The towns and villages along the route have either been destroyed during WW II or afterwards by the Red Army. So mostly I have seen a lot of drab housing complexes in a rather shabby state. Sometimes some old remaining buildings have been renovated but these historical sights look strangely out of place in the post-communist surroundings. The R1 passes through Grudiaz (formerly Graudenz) which is a prime example. The old castle complex has been renovated and was teeming with people on a sunny Sunday afternoon. But in order to get into and out of town the R1 follows endless rows of depressing housing complexes teeming with people that sometimes even looked rather scary. Very few pre WW II houses were left and they looked so bad that I was surprised that people were still allowed to live in there.
To sum it up: the R1 in Poland is definitely not a recommendation. From my point of view there were only two good aspects: the R1 surprisingly well marked - and stealth camping has been easy.
But I am off the R1 now and things will improve in my next post...