Has anyone used these?
http://www.amazon.com/QuickZip-Crib-Zipper-Sheet-White/dp/B000XV7X4W/ref=sr_1_1?s=baby-products&ie=UTF8&qid=1367369157&sr=1-1

They get really good reviews on Amazon, but don't come in cute patterns and only a few colors (I know-- the big things). Has anyone on here used them? I'm intrigued...

"Clouds and Stars Quick Zip Additional Top Sheet - White

The world's easiest crib sheet! This innovative two-piece QuickZip Crib Sheet is designed to be simple, safe and stylish. The top zips off the base for easy changing. Place the mattress in the zipper base, lay the flat mattress pad on the mattress and zip on the top. When the Zipper Sheet is soiled, just unzip it - no need to remove bumpers - and slip on a clean one. 200-thread count, 100% cotton, fits mattresses 52" x 27" and 4.5"-7" thick - standard crib and toddler bed mattresses."