NAPs these days are stable, scalable, and useful.
IXs (there were only four NAPs, and i'm too old and lazy to play droid terminology drift) have pretty much always been scalable (for the then current meaning of scale) and useful. though i have admiration and sympathy for folk such as steve, keith, mike, et alia, who have had the task of scaling them (it always looks easy from the sidelines). but, wearing a different hat, i am aware of issues on some of the large exchanges where one is suspicious of layer two origins.
Picking your peers carefully - which is a requirement for public or private peering - helps.
this does not isolate one from the majority of layer two messes, the subject of this thread. on the six, i had just such a problem caused by a sloppy-but-arrogant weenie with whom i had no desire to peer. and guess what caused it, switch on the ix. randy