This was my first usage of AirBnB, so one can imagine my trepidation. I was there for work on Schofield Barracks, and while my coworkers were obliged to spend something like $6k per person on stays at the Marriott in Waikiki, I opted for the $88/day rate of Barbara's charming garage apartment on the North Shore. In short, my stay surpassed expectations. The location is close enough to Hale'iwa that you can take advantage of the town (food trucks galore!), but far enough that you are not inundated by tourist traffic. It is directly across from a school, but that did not present any issues. The internet is plenty fast, and there's plenty of space in the room itself. The kitchen is well-stocked, and the bathroom/shower room has everything you will need to survive your North Shore adventures.
I suppose a complaint could be made for a lack of air conditioning, but A) there are plenty of fans with outlets available, and B) the wraparound screen windows provide ample airflow. My stay was during the hotter months of the year for Hawaii and I had no complaints.
Make sure to take advantage of the hammock Barbara will offer you--it's in a perfect spot and incredibly relaxing.
Mahalo!
Tom