I also agree that taking the train is the single best way to get around. You can always rent bikes and go for easy rides (it's pretty flat) on the country side without even having to go more than 20 km. Especially in Belgium.

Driving in Brussels or Paris would really, really ruin things for me. I've driven over about a third of France, but I have horrible memories of driving in Paris. The Velib' however is so much fun!

I'm very envious!

Some lovely Belgian images from my friend Hugues, perhaps the first photoblogger, who's still going strong after 14 years: http://www.fugitif.net/