@aaric - Is the rattling a common occurrence with segmented housing on internal frames?
Any where segmented housing contacts the frame, you'll want to protect the frame. From personal experience with iLinks, the aluminum ridges will quickly wear into the paint and frame otherwise. Heat shrink works decently. There are quite a few cable protectors available, and iLinks come with some ugly orange/red ones that work well.
Also, any where the cables cross, if they are next to each other they will rattle, and wear off the finish of the cables unless they are protected. This can be frustrating as you have to take into account where the cables are when you turn, as well as the effect of bouncing over rough roads.
For me, having the possibility of aluminum segments rubbing inside the frame where the damage couldn't be seen or easily monitored made segmented cables unacceptable. For what its worth, my frame has a direct mount rear brake under the chainstays/bottom bracket, so it has more likelihood of this occurring than a normally mounted brake given how the brake cable is routed, and that it uses a full housing run. My old venge for instance didn't run housing internally.