I've never had a cable catch on anything. I think the way cables are angled to go into tubing looks rather ugly, and much prefer a neat, colour co-ordinated outer.
Another factor to put me off is the potential for rattles with internal cables, which I understand on some brands is a very annoying issue.
I'll admit if I was in the TdF, then every marginal gain is worth it, but for mere mortals, there's a certain element of the Emperor's new clothes to the concept of internal cables on consumer bikes. Having also inspected a few, the seals on some don't look so efficient, so as well as possibly introducing an element of structural weakness in having a hole in the tubing, there's also the potential for water ingress.
It's yet another thing sold as innovation but really it's more so manufacturers can justify a new model.