I think this was mentioned earlier, but it doesn't make much sense to sort filament by printer. Unless the material was specifically optimized for that machine, all ABS and PLA filaments can be used on almost any FDM machine. Just something to think about.

I think nylon or a flexible material is great next step for this site. I definitely get that this site is trying to fill the whole seller niche by offering discounts for very large orders (up to 48 spools). This is great, but to keep ahead of the growing demand for materials other than ABS and PLA, nylon and flexible materials should be next on the list. Other materials than these would be nice, but are more specialty materials that wouldn't apply to a large majority of prints.