Hi jkrit
I rode solo to Denmark, Norway,Sweden,Finland,Russia,Estonia Last year, and my girlfriend who i met in Oslo on the trip is Polish and lives in Poland.
What exactly do you want to know? it is all pretty straight forward, I agree with the previous comment on Norway, spend as much time as you can there as it a beautiful country, i think you would appreciate the hills and mountains coming from Holland

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but make sure you take your winter waterproofs, the weather can change from one extreme to the other. Tallin in Estonia is worth a visit, as is Helsinki.
I found the Scandanavian countries very clean and safe as was Finland and Estonia. people claims of Norway being prohibitivley expensive i found personaly to be an exaggeration, i live in London and found the prices to be slightly more in norway than they are here, obviously if you want to eat and shop in tourist areas then you will pay a premium, but the alcahol is very expensive.
I have been to Poland twice in the last six months but not by motorbike, as i said my girlfriend lives there, so if you want to know anything ask me and i will found out from her any information you want to know,
Krakow is nice, and if you can handle it a visit to Auscwitz is quite a sobering and sombre place to visit. There are some amazing salt mines in Poland which you can explore , i forget the name of the place where they are but i can find out if you wish.
The majority of the people in these countries speak English, i never had a problem getting around, it maybe a bit more dificult in Poland communicating with the older generation.
Another thing about Norway, don't underestimate the distances involved in travelling there, if you ask a local person how long for instance to do 500kms and they reply 'ten to twelve hours', listen to local knowledge, don't think you know better, you will be riding for miles and miles and miles of hair pin bends in some remote places, and you will have to take ferries over fjiords etc they don't have a motorway infrastructure like your country or of the european countries around you, they don't need it with a population of four or five million people and a large land mass to live on, and that is what makes Norway so spectacular. I have never visited a country twice in successive years, but my girlfriend and i were so impressed with Norway we are going back this year.
Hope this helps