These shorts are part of a pant-system with zip-off legs.
For a 3+ day hike, I just take the one pair of shorts and wear them most of the time. If things get really wet, I will wear my thermal pants for a day while the shorts dry out. It's been working well for me.
OK… time for something personal. The shorts have an inner liner, so I find them comfortable enough to wear without underwear. No grundies, no extra ounces adding up. This little tip does not work for Theresa!
At 8 oz they aren't super-light, and I wonder if there is a better option, but the versatility of the pant legs, makes it worth it for me.
Shorts and pant legs available from REI for $64.
Theresa wears a similar set for women – I think the REI brand ones for $55.