I've got two little angels when it comes to travel - they've certainly got the routine down these days too. From the day we got them, we've been taking them places - mostly to my parents and back so they don't always assume it's going somewhere unpleasant like the vet's. We also leave their crate open to them at all times. I've caught one or both of them sleeping in it at times.
For the most part, as a result we've got quiet travellers. They even know that on long stops, such as when waiting for the ferry they'll be let out of the crate to stretch, use the box etc. I've ended up with sleeping balls of fur in my lap a few times, and there's nothing sweeter.
It's interesting. One of the two will deal with the leash and harness - even seems to want to go out though once outside isn't too certain. The other vanishes at the thought. I'm working with her on that a bit though (treats while wearing it etc). I'd love to get them both a bit more used to it.