I bought these shoes several months ago for a weekend of record rainfall in Portland, OR.  I walked 5-7 hours each day in these shoes and my feet stayed perfectly comfortable, dry, and warm.  I wear a size 6.5 and bought a size 6 since this is my normal Crocs size.  The shoes stretched just like the normal crocs, but I think the decision to go up a size due to the liner is dependent on your feet.  My feet are narrow so it worked for me.  I've taken these shoes to the snow, rain, cold, etc and they hold up great.  The liner is easy to take out and wash.