My gauge was totally on, but when I finished CPH it didn't match - I had to stretch it quite a bit to get it wide enough, and the length was too long - I coulda cried but it all came out beautifully in the blocking and I've never been out of it since! see http://socherryknit.blogspot.com/2007/04/central-park-hoodie-complete.html
Which just goes to show that stupid gauge swatches lie!
grr! But there is the failsafe of a much wider button band [i did this] if it is too narrow, and i really don't think it could be too long - but that's maybe just me.
If i did it again i would knit the front panels wider and use the sleeve shaping and sleeve for the size up as these were quite snug.
The circs aren't needed til picking up for the hood so you can cast on! Unless youre planning on doing it in the round, there is no knitting in the round, she just used circs cos it's easier for the hood bit than straights.
Can't wait to see - the CPH KAL is still alive and kicking by the way http://cphkal.blogspot.com/