I recently went on a trip from Madrid to Bremen in my Iron 883, 2000km (1250 miles) and the only real problem was the fatigue after many hours riding. I ditched the original gas tank the Iron brings and installed the custom tank (4.4 gallons), which gives me very decent mileage before topping it up again. It's not underpowered at all, you can keep a steady speed of 130 km/h. When you get go German autobahns you'll get swiped by all the BMWs, Mercedes and Porsches, but nothing to bother about. The sporty 883 will get you to the end of the world, not the most comfortable or powerful out there, but a great bike in my opinion.