what's not to like? i day hike in my board shorts. though i live in hawaii, so all outdoor activities are done in board shorts. materials are plentiful (many having a small % of spandex), so it is a good idea try them first before buying. also, cuts differ. some are a bit baggier. others, lean. i tend to like a tighter fit. and despite the trend toward longer shorts (and terribly ugly prints), all of mine stop just above the knees. i wear my t&c shorts regularly for hiking.
i haven't had an opportunity to do multi-day, but i could definitely imagine staying comfortable for several days of backpacking in mine.
also, i should mention that my birdwell and katin shorts are the FASTEST drying materials i've ever worn. they're straight, super-strength nylon. when i swim with those, they're typically dry within 5-10 minutes. though, they have a more traditional surfing cut to them, and many would not find them as comfortable as the current offerings from the big surfing companies.