Hi, I thought I'd post an update, in case anyone else is interested in this jacket...
I went ahead and bought it. I got an XS (I'm usually a S) and it fits really well - so it pays to look at the measurements rather than sizing.
Its super lightweight, looks great and has stood up to small showers so far (haven't had enough rain lately to test it out on big showers). Its really nicely breathable.
I'd highly recommend it to anyone who is considering it.