Purchased February 8, 2013
I work on a farm and ranch and handle fence posts and barbed wire and thorny brush and building materials frequently.  I needed tougher pants than plain jeans.  Jeans snag and tear and wear and rip at and above my knees.  So I ordered a pair of Riggs to test out.
I'm pleased.  The threads are big and heavy and the weave is very tight.  So far thorns can't get a purchase on the fabric to snag.  The only snagging I've had is the little side pockets will sometimes get hooked by the lower kitchen cabinet knobs but that is not the pant's fault.  The fabric and weave is very wear resistant so far.

Five stars, from me.

Just a heads-up.  As I said the threads are heavy.  That means when you kneel onto your knees you can feel every thread mashing into your skin.  It can hurt.  Especially if you're a big guy like me.  But pain comes with the territory of manual labor, so it seems.  "C'est la vie"