I recently had a 4kw solar system installed with the iBoost and my system is split on an east/west roof. The iBoost works on our system and yet we never produce 3kw at any one time. I’m very happy with my system, and yes there will be days when the iBoost won’t work, so what.
For what it costs, I think its a worth while benefit, why “waste” the unused energy that you generate when you could benefit from it. In fact there is a new version of iBoost, iBoost+ which has a “Buddy” which allows you to monitor how much surplus energy you are generating and therefore when its best for you to turn on appliances so that you can use that energy.
Unfortunately, its not backward compatible so its best to have it installed from the start.