A little discussion on OM (http://www.outdoorsmagic.com/gear-news/just-in---rab-boreas-pull-on/8049.html & forums.).
Seems like will have to be slightly careful of it as a windshirt replacement and certainly not a 'tough' conditions soft shell - far from totally windproof, no DWR by default, very basic hood/no cuff adjustments etc.
(thus the very good price!)
More of a thin, wind resistant mid layer or something. Potentially useful as that of course.
Their 'deluxe windshell' is the alpine jacket, with a proper adjustable hood (and a really nice one going by the pullover I had), pockets etc and a similar overall weight. Slightly more expensive of course.