I originally bought this jacket to keep me dry in occasional downpours, but I've since moved to Miami and this jacket is basically my best friend. It can be a bit sticky when it's really hot, but the underarm vents help a bunch with that. It even worked as a wind breaker while exploring the Pacific coast.As far as fit goes, I'm 6'0 and really slim, so finding a jacket that doesn't either swallow me or look like I grew out of it 10 years ago is kinda hard. I bought a small and it's perfect for me.
I picked up this jacket a few years ago for backpacking. It has been very durable, material an seams have held up great through a lot of abuse even a few rounds through the washer. Most of the features you want in a technical shell. Huge mesh pockets on inside are great for stuffing gloves, goggles, or well anything, but so deep retrival can be difficult with jacket zipped even part way up. Main zipper has begun to get stuck due to extra fabric on inside, note this is after years of abuse. Sizing is true but think about your plans for layering and make sure you leave room as this is a shell not an insulated jacket. Overall great product and solid construction for a good price.
I am extremely satisfied with the waterproofness of the marmot material. I'm a 6'1" 175lb dude, and I got a medium. A good choice except when I'm at full reach and the sleeves pull up a bit. It has a great athletic cut that meshes well with packs of all sizes, and doesn't have much excess material to get snagged. The main zipper is horrible. Very rarely can I zip it up without hassle. Something always gets caught. It's a plastic zipper, so I expect breakage eventually. Also, the sleeves are getting fuzzy near the cuffs where my wrists rest on stuff. Looks sharp, but pretty spendy.
Sizing - I'm 6' 160lbs, medium fits well. Looks - Very good. People compliment me on it, which is unusual for me. Performance - I've had it for two years. Sheds water like a champ. If you wear it for a really long time in a downpour it seems not to breathe quite as well. But overall it's everything you could ask for. Function - Lots of useful pockets. Zippers are smooth, pitzips are nice to have for aerobic activity.