I love the concept - my only problem with it is that the six starter themes (swatches) featured on the site aren't really attractive enough, more like failed experiments... it could benefit from a design-off where popular designers create a swatch with their own take on the Bootstrap, and submit it to the site...

PS: Overheard on Twitter (https://twitter.com/#!/bcherry/status/169960949967626241):

New web dev trend: "Yo dawg I heard you like Bootstrap so I made bootstrap for your Bootstrap so you can bootstrap while you Bootstrap."