Great, whatever works for one. Definetly less hassle and cost.
Nowadays there are so many possibilities for adding ambient sound to your IEM mix, for example most of the small monitor mixers from Midas, Behringer, Roland, Aviom, etc… have built-in ambient mics. If one of those devices ist positionend strategically well on stage it is posible to feed these ambient channels back to the console and into everybody’s In-Ear mix.
Another benefit of the ASI system for me is that when rehearsing I can dial in the volume of my acoustic drums without micing them and add whatever signal I need/want in my ears, eg. a click or backing tracks.
No matter what the situation is, the positioning of the binaural mics right at the ears provides the most natural listening experience.