I've been using the same Pearl Izumi bike shorts for at least 15 years. They always fit the same and the ride is extremely comfortable. It's what I've come to expect from all Pearl Izumi products. Excellent quality and workmanship.
These are my everyday riding to work bike shorts, reasonably priced (way better if you can hit the sale). Knock them around and then wash them out and they're ready for another day. The Levi Strauss Blue Denim pants of bike shorts built to take it all. I love 'em.
They work well. I have not ridden them over 50 miles. I am 6' 185lbs, wear 33 waist, am average shape and the size M fits nice and snug. A size L might fit more relaxed. I would not buy super cheap bike shorts, they don't not keep you in place. These do.
Good value for the price for cycling shorts I wanted for moderately long road rides (3 - 6 hours in the saddle). Panel material is robust, and padding provides a firm and stable foundation. Ordered large size based on measurement recommendations on the web site and feel constricted in the crotch - will be exchanging for XL, but everything else (waistline & legs) felt fine. Maybe add a little extra room down in front?
As others have noted, Pearl Izumi shorts run small. I'm a 30, and the WBW size chart says a small should be 29-31.5, but these are borderline tight. (A medium in PI is typically too big for me.) Solid construction, but has an annoying stiff seam jutting inward that sits right on the buttock-will likely soften up with a few more washes, but this is the largest, stiffest, most intruding seam I've ever seen on the inside of cycling shorts.