I LOVE LOVE LOVE LOVE the YLI thread!!! For hand quilting, make sure you get the glazed cotton thread. Can't stand C&C thread. The Guterman thread is OK, and yes, it is thinner than the YLI.
I can't find YLI hand quilting thread locally, and have to order it online, but that's ok - I'll do it.
I agree, I wouldn't want to use a glazed cotton thread in my sewing machine....