I've done quite a bit of cycling in Europe: Italy, Spain, France, etc. And I've never taken my own bike, even though I have a really nice folding roadbike.

First it was the cost of checking it on the airplane---but now I fly so much that they wouldn't charge me anyway. Even so, I prefer to work with a local shop and rent a bike in the country I am visiting. It's fun, I get to try a lot of new bikes, and often find that the shops are really helpful in setting my up with something.

In fact, the last two times in Spain, they didn't charge me--they just asked for a local cycling jersey from California...and then they gave me a Spanish one. Pretty cool.