i know it's different geography but we drove across europe this summer - bruge, cologne, munich, berlin & paris. got the ferry to roscoff. i'd do it again in an instant. was an amazing holiday...anyway...my one piece of advice - get a good GPS, make sure it has all the 2008 european maps and you can't go wrong. we are guided to perfection by ours - it'll be the best money you'll have spent.
another few tips - petrol across europe is very expensive (circa €1.40 a litre) so be careful. also the tolls in france are horrifically expensive. that saying, the worst journey of our whole trip was getting back off the boat and driving back to dublin. after being across europe, it really hit home how brutal our roads/general infrastructure/drivers really are.
have an amazing time.