These routes are almost identical in distance to the SFO/LAX/SNA-EWR routes that CO has operated using narrow bodied aircraft (737 and 757, both with the same cabin width) for years. You rarely, if ever see complaints about that, and most of their competitors do the same on transcon routes. What makes west coast-Hawaii any different?

The cost per seat per mile of the aircraft that CO is using here is significantly lower than the ancient 767s that several other airlines are using. This is a huge advantage for CO IMHO. And to add - the vast majority of the general public doesn't give the aircraft type any notice when booking a flight - they base their decision on price, and maybe schedule.