ThinkPad X touch series are great, as they're ThinkPads (which still seem to be the highest quality, despite Lenovo's efforts). The X series are laptops first, convertible tablets second. There's also a ton of convertible tablets made by plenty of vendors. In 2005, Toshiba made some nice ones. A few years ago Fuji had some neat ones. Nowadays it seems everyone has some lightweight convertible available. On the low end, I've heard great things about the new ~$400 Asus Transformer.
