The Ellipses are really stiff, and the bladed spokes probably help a bit. The rim weight will hurt you on a standing start, but if you're just maintaining a steady speed it doesn't matter much once you're up to speed. Clinchers also seem to consistently measure out at lower rolling resistance than tubulars, even though they generally run at much lower pressures. The difference is generally attributed to the lossiness of the glue, which stays pretty flexible unless you're using real shellac, and I don't think I've seen anybody shellac their tires on since I've been racing.