I took a hot glue gun and glued some fabric to the top of my box springs because I'm lazy.
It peels off easily for washing (which I admit I don't wash it very often - again, lazy. I'd rather quilt!). I think when I'm ready to change the dust ruffle, I'll glue sections of Velcro to the box springs and the fabric, so it can just pull off. I kind of like the idea of putting a fitted sheet on the box springs, but then that ugly frame would still show. So I'm back to dust ruffles.
Regarding how low I like my quilts to be, our bed is a king size extra-deep mattress with a pillowtop. I feel like the Princess and the Pea when I climb up on it at night. So a king size quilt at 110" square hangs to the bottom of the mattress on both sides, which is just fine by me.