The only potential problem with them is spare parts. Availability is ok at the moment and giant sell a lot of bikes so hopefully replacement parts will be available in the future. If the worst comes to the worst you could allways get someone with a lathe to make you an insert and use a conventional headset.

As for perfomance it is after all just a normal headset in a slightly larger head tube so both the bearing and cup can fit in the frame. The conventional method of having the bearing outside the headtube is really just a relic of cup and cone loose bearing headsets.