There was a massive thread about Cos a few months ago you may find useful.
It seems to be a very marmite place on this board. It markets a definite style aesthetic; minimal, androgynous, simple lines which is not to everyones tastes or body types. However, just because Cos has decided to present themselves this way, doesn't mean individual items can't be worn to suit other styles. e.g. they do basics very well; plain t-shirts and shirts slim or loose cut, round or v-neck cardigans of varying lengths and weights of knit, plain trousers in most cuts and rises. Their USP, to me, is how they twist and fold the material to create some great details, how they cut the fabric to make it hang slightly off, always differently to the usual frills and pleats most shops tend to design with.
It's also one of the few high street shops selling natural fibres at an affordable price. Their 100% wool knitwear is IMO some of the best on the high street and definitely good value for money when compared to the rubbish quality the likes of Whistles or Toast (nowadays) put out at a higher price. I think the quality meets the price.
BUT - the sizing is all over the place and in pictures and on hangers doesn't do some things justice. You really need to try things on. Luckily their changing rooms are nice, and the staff never rush you and let you try loads on.
Online service is great and their customer service easy to get hold and helpful, I've found. But they rarely do free delivery, and refunds can take a few weeks as they ship back to Sweden.
Oh, and it's part of the H&M group if you didn't know, or that makes a difference. Same as &Other Stories.