I have several older pairs of Ex Officio pants and they have held up well.  The newer material is lighter than the old cotton they used before.  The newer pants are more comfortable and seem to hang a little better on the legs.  The buttons used to be a problem - looks like they cured that issue.  The fit is nice but the 36 was too small for me so I returned them for 38 and they fit perfectly and stretch when you move.  Amazon was great on taking the returned item without a hassle which is a big reason why I shop at Amazon.  Great service and I did not have to talk to any snotty service operators.  All done on the net to my satisfaction and this means I will be doing more business with Amazon.  If you travel - the convertible Ex Officio's are great on a trip.