If the jeans have 1 or 2% spandex in the fabric the fit is MUCH different than 100% cotton jeans.  The stretch jeans will feel tight and true to size when you first try them on, but as you wear them they stretch out enough to add another size.  I have 36 waist 511 jeans which are 100% cotton and newer 34 waist 511 jeans with the stretch fabric and they fit almost exactly the same.  It's basically vanity sizing (making you feel good because you can go down a size).

Also, ordering a much longer inseam is cool with these jeans since you get a nice stacked look above your shoes.  You won't step on the back of your jeans unless you're wearing flip-flops.

Great pair of jeans for $35 range.  Fabric isn't all that but fit can't be beat.  Not just for skinny guys either.  I'm a big guy with big thighs (6'2", 205 lbs) and these jeans fit just right.  Big guys don't have to wear baggy jeans.

UPDATE 4/26/11:  The SAND DUNE color is listed on website as 98% cotton, 2% spandex. It's actually 54% cotton, 46% polyester in this color.  The fit is completely different than the same size in a different color with 98% cotton, 2% spandex.  Fabric is doesn't mold to your body at all.  If you order SAND DUNE you may need to go up a waist size.