They do have a range of fabrics, from lighter weight linen up to heavy canvas. All of what I've purchased has been med weight/canvas material (that seems to be the majority of what they offer). I would use it on the back of a quilt with no hesitation. I've even paired some with denim on a quilt top.
I can only speak to the med wt/canvas material - it washes well with minimal shrinkage or wrinkling. The colors stay bright and the fabric gets softer the more it is laundered.
I haven't bought any of the solid fabrics - I'll have to try some next time I'm at Ikea and post about it if someone doesn't beat me to it in the comments. Unfortunately, they only sell the fabric in-store. Though you can usually find some (higher priced of course) on ebay or etsy.
I think the odd size of 59" is because they are starting with centimeters (150 cm = 59"). If they made it 60" they would be selling the rest of the world 152.4 cm - odd indeed. : )