I'm in the clydesdale category and often carry a decent amount of stuff to add to it. I have a Salsa Delgado Cross 700c 36h on the rear which I find holds up very well. Heavy gauge spokes and a good wheel build do the rest. What I put on the front seems to make very little difference, so I usually run whatever reasonably priced double walled rim my LBS has around.

One lesson I learned the hard way is to clean your rims fairly often if you ride a lot. Road grime on rims and brake pads wears out the rim making it thin enough you will start to get cracks around the eyelets. I went through my first Salsa Delgado rim in less than a year because I didn't know that. With more religious cleaning I can get 5-6K miles or more.