I am a cheapskate and use sheets for lots of sewing projects -- the yardage really is amazing when you get a super sale price! Having said that, I don't "love" sewing with sheets because I've found that they tend to fray much more while working with them. But I still use them when I find good deals. Now I have not used microfiber sheets at all but I have some and know what they feel like. They would be a great lightweight fabric for a cathedral windows quilt which can get heavy with folds and layers, but my question would be will microfiber actually hold a crisp fold? That's what I would check first. Maybe try ironing them with and without steam and starch and see how they behave before you invest a lot of time into cutting. I think I would test them out on a couple of sample blocks first and see how they perform! I'd love to know what you discover! I'm all about thinking outside the box and using new materials!