Mainly use it for running & other highly aerobic activities. Wicks well, highly breathable. Can wear it a few days in a row for running, has little odor (unlike cheap brands). I haven't had a problem with stink setting in & lingering after tossing it in the laundry, always comes out fresh. Light weight zip neck doesn't get in the way & fold of fabric keeps zip from rubbing. Works well in the upper 40s to 50s w/ little breeze & on windy days w/ a Marmot Ion its perfect. Wouldn't use it as baselayer under pile fleece as it tends to hang on pile, would use a smooth silkweight like capilene 1 instead.

Ion is a great wind & light rain jacket. Definitely for the active sports of running, hi-tempo riding, & XC skiing. Don't try & sit in it at a December Chicago Bears game. I'm 5'10" & ~ 165lbs, it has a technical fit, but never feels restrictive. My Men's medium weighs 4oz. For those windy days or rides, its a very versatile piece when you choose to layer it w/ various weights of wicking base layer. I found mid 50's w/ capilene 2, 40s w/ capilene 3, & powerstretch for the 20-30s to work best for me. I know its cliche, but it really does work & keep the wind out w/ its tight weave. It moves body moisture well, haven't had condensate on the inside at all. Haven't had long enough for durability issues, but I wouldn't run into thorn & bramble patch with it, nor would I rock climb in it. Has a soft hand, drapes well, matte color (not shiny) packs into its chest pocket, tech fit eliminates need for waist cinch cord, has longer tail, has funky foam hood drawcord (keep wgt down?), hood rolls inward to become part of collar w/ strap that snaps. If you already own tons of various weight baselayers, this maybe right to keep winds off, but if you already own Marmot DriClime jacket/wind shirt this may be a redundant piece.

Have had the LS silkweight for 9 mo. now & the shirts have held up very well. i have not had any lingering stink problems like I've had with other cheap dept. store brands. The shirts always wash out fine even after 3 days of use, stains release too. Haven't snagged yet, but I was inside out every time. Wicking properties are great. Does fit a bit small, would order next larger size next time.