interact much with Estonia, Latvia and Lithuania.
Lithuania is probably the most visited of all these and mostly Vilnius (Wilno in Polish) - one thing: proximity; secondly: Polish heritage - besides Vilnius, Lithuania is fields, forests, lakes and the Baltic - we have all of these in Poland
for Latvia and Estonia the main attraction for Poles would also probably be their respective capitals (the language barrier in the capitals is the least I would presume because more people speak English there - the national languages between the countries are very different - even Latvian and Lithuanian which are related are not quite mutually intelligible)
I don't personally know anyone who's been in these places, though - but I live a secluded life on the other end of Poland (though I have seen videos on youtube made by Polish travellers to Vilnius a couple of years back)