This arrived very quickly and I have treated it to an outing to the gym almost instantly, my first impressions would be that it might be a bit tight - it is figure hugging and certainly doesn't leave anything to the imagination. So, maybe, as with a lot of these active wear items, go for one size bigger if you're unsure of how "out there" you want to be! Or you may want to use it as a base layer and wear something over it.
However, it was very comfortable to wear (once you've removed those annoying extra large care instructions) and feels very soft to the skin.
So far, I've only used it in the gym so don't know how it would fare outside in the rain. It is pretty lightweight and although the shirt got damp, your skin still felt dry. It was never restrictive and didn't chaff anywhere.
Hope this helps!