I've got a pair of Chinooks. For me they're pretty much strictly a late season pant, but I run pretty hot when I'm moving around. I wore them mid October this year, not sure what the temps were during the day, maybe 10*C, but I was absolutely sweating my bag off while hiking around. Had the legs rolled up and vents open and was still uncomfortably hot. They were great for early morning and late evening, and fine for sitting and glassing, but too warm mid day.
I wore them again for a week end of November and they were fantastic. Temps were around freezing the whole time. If I got warm moving around the vents would help a lot.
For me, if the temp will be much above freezing I'll be wearing something lighter for next year, possibly paired with a zip off base layer. For later season stuff, the Chinooks are great.