I've got the Forté tubes on my Look, and haven't had any problems with them. I'm one of those Freds who keep the nut on the valve stem, because it serves a purpose - it gives you something to grab onto when you pull the pump head off, thereby reducing the chance of pulling the valve stem out of the tube. It also holds the valve stem against the pressure of attaching the pump head when the tube is almost empty, as it is when installing it or fixing a flat.

Having said that, any tubes I buy in the future will have smooth valve stems, since that eliminates the need for nut in the first place - the pump head just slides right off.

BTW, either Performance or Nashbar (forget which) has the cheap Michelin tubes on sale for $3.99.