Shame on me. I missed the european site of TeleNav. So, TeleNav already offers navigation services for Western Europe, from Norway to Greece (without Balkans) and from Portugal to Austria.
TeleNav offers its services in Europe for BlackBerry devices only at this time. The software itself isn't charged, but to use it, you have to buy a license, ranging from a 3 months license for 27 Euros (9 Euro/month) to a 18 months license for 121,50 Euros (6,75 Euros/month).
A free trial period of 30 days is offered.
Map coverage seems OK, although the map preview doesn't show things like one way roads, so that I can't determine too much details by just looking at the maps.
Although TeleNav might work well with the iPhones data plan or even using WiFi, one fact leaves a bad taste in my mouth: what about holidays? Either, you use prohibitive data roaming or you just don't use TeleNav at all...
As I'm abroad on a regular base, I would prefer a road navigation solution that stores its map on the iPhone itself... We'll see, hopefully in the near future ;)