This shirt is a good travel shirt because it is very light (can layer even when weather is warm) and is hand-washable and will dry overnight.  I bought it in the hopes that because it was button down, it might be appear more "formal" for dinner, etc than other shirts.  It is quite loose fitting.  pockets are a good size.  Compared to the Columbia Titanium which I also own 4 shirts, in the same size (medium), the arms are about one inch longer and the body of the shirt is much looser.  the shirt, particularly the black one, is suitable for more "formal" dinners if you layer a nice sweater over it.

however, without a sweater, my wife thinks the Titanium looks more "formal".

I have since bought two of the Tamiami small and they fit better--about as good as the Titanium medium.  so the shirt definitely runs "larger" than the Titanium.

I wear a 40S sport coat.