Cast another vote for the Tilley. Mine is about 15 years old, and still going strong. I've worn my Tilley at Point Barrow, Ushuaia, and lots of places in between. It's truly an all-season, all purpose hat. I do wear something warmer when the temps get below freezing.
My hat is one of the large brim, all-cotton models. The Tilley Hat was originally designed for sailing, so they stand up to hours of soaking rain. I have not felt the need to try the newer cotton blend designs or the ones with the extra ventilation.
The strap that holds the hat on your head from the back of your skull as well as under the chin is an under-appreciated feature. The strap really does work, even in Patagonian gales.
Chip Haven