Most panels are perfect for One Block Wonder/Stack n Whack quilts. The only problem is that they may not give you enough fabric if you just buy 6 and layer them. You may have to buy multiples of 6 to get a bigger quilt.
It is fun to buy one extra and piece that into the backing. I am definitely not a fan of putting a whole panel on the front as I think that takes away from the beauty of the hexagonal blocks, but it is fun to see the panel on the back.