Switched to breathables for the tube many moons ago and simply wouldn't go back. Any wader type can leak and yes breathables have a tendancy for seepage around the seams (as Jim will confirm following my damp right leg after Park), but this happens when normal deep wading with this type of wader just as much as when tubing. (Ok yes you're in the water longer in the tube)
Re-sealing the seams shortly after buying cures this. Yup i know a new, or fairly new pair of waders shouldn't need this but you'd be surprised just how many makes (even the dear ones) you get sepage via the seems on. Quick blast of aquasure and yer set for a good while though.