Last summer I flew to Lithuania and I was really happy with it.
It was easy to get charts and info on the internet and they have a friendly briefing office! There are some fees at the bigger airports but they are small and compensated for with a very low AVGAS-price. It was about half a euro cheaper per litre than in Sweden.
Check the price of AVGAS if you are flying in to a smaller field though since they can have other prices there.
Sweden is pretty easy as some has mentioned. You do not really need a flightplan unless you want one when flying within the borders. The AVGAS is still ok priced compared to other European countries. The airfields are plenty enough and there is something for everyone when it comes to scenery.
What I think we also should take into account for the local residents are the charges from the CAA to own an airplane and for having a license...
Even though we all are EASA there are differences.