To this comment:
"It's a good June-August jacket but a little light for shoulder season use."
I would say that's likely to be true for a lot of folks, but not universally true, and as someone else suggested, it depends on various factors. Your metabolism, your "hiking style", where and when you're hiking, whether the weather turns out to be 'normal' for that time and place or not ... etc.
"Style" --- I used this jacket as my warmth layer when I thru-hiked the CDT, coupled with a thermawrap vest. The first month or so I was in snow more often than not. But a common thru-hiker approach to staying warm is to crawl into the sleeping bag and do everything in camp "half in the bag". I.e., no sitting around in camp on a log, singing songs and toasting marshmallows or the like (at least when it's cold).
This is a very warm piece of gear for the weight and bulk. I also have a Montbell Alpine Light parka, and while it is of course much warmer, it's also a lot heavier and bulkier. The UL Down Jacket is a great piece of gear to combine with other layers, and something small and light enough that I'll toss it in a daypack even on hikes when I don't expect it to be very cold.