You could always ask the mechanics at the LBS where you saw it how easy it is to rethread the cables on that bike if one were to break. Out of curiosity, I did some checking. Some frames make it real easy, with others it's trickier but not ridiculously so. There's an old thread in the mechanics forum with a bunch of tips.

One interesting one for a difficult frame involved taping over all the holes in the frame except for the entry/exit holes for the cable you wish to thread. Run some string into the entry hole and use a vacuum at the exit to suck the string out. Another option was sort of the reverse, - use an air compressor with the regulator set at about 10 psi to blow into the entry hole. The string will magically appear at the exit hole.

Other people used things like spokes to fish a string through. Another guy said that many frames that appeared to be very difficult to thread cables through suddenly got very easy once you removed the seat post.

I'd personally like internal cable routing but I'm fine with external too.