I have good experience with Samsung Q1 Ultra. It has no keyboard, which I see as advantage and is manufactured in prime quality and has cradle. Biggest problem is that my version has Windows Vista, I need to donwgrade to XP. There's probably no chance to run Linux on it, which is pity.
I was also testing Mivvy UMPC, which runs Kubuntu, but is based on VIA C7 and facing too many troubles. And of course, case quality is not good.