Sizing: I am about 5'5'' and 140 lbs and got the medium which fits well. The style/cut is relaxed and loose.
I find it a tiny bit too low-cut for my personal preference. When you bend over your bra will show, which isn't a big deal in some situations but if you want to wear this backpacking while traveling in for example a country where women dress more conservatively you might find it too revealing.
I recently got the Retreat Tank in Sterling, which is a very light, shimmery grey colour. I personally would've preferred a darker grey but the existing colour is ok too.
The material is soft, silky and ultralight.
I like how the back of the top comes up to the base of the neck for sun protection.
The straps are wide enough that you can wear a regular bra under it.
The gathering at the neckline is a nice detail.
The edging detail around the neckline and arm holes is unstitched, not sure if this will be a problem with loose fibres coming off or not, as I've only had the top for a few days. Will have to see if this becomes an issue but so far I like this versatile top.
I've been wearing it in very hot sticky weather and it feels good.
Could be dressed up or down. A good light travel piece.

For help with sizing, I am 5'5'', 140 pounds, bra size 36B or 36C and ordered a Medium. It fits well. It isn't a fitted style, it's loose-fitting which I like since I am wearing it in very hot weather and it allows air to circulate well.

The orangey-coral color (Ember) is very bright but I like it. The fabric has a lovely natural subtle sheen to it and is very lightweight, soft and quick-drying. I have worn it a few days in a row in hot sweaty weather cycling a lot and it doesn't smell.

Support: depending on your bra size and your body shape, you may want/have to wear a bra underneath this tank even though it has a built-in shelf bra. This is because the top is quite low-cut (don't buy this tank if you don't like low-cut tops!!) For this reason the top seems more geared towards the city end of the scale - for going out - and it can be a flattering top. But if you are a B or bigger cup size and want to use it for hiking, yoga or other sports it's a bit too low cut and unsupportive without something underneath.

The racerback and gathering at the neckline look good and overall I really like this top.
I would give it a 5th star if it were not quite so low-cut and unsupportive for curvy women.