When discussing waterproof clothing which is really waterproof, but doesn't make you sweat during exercise or touring, my colleague and friend, Keith Dickinson http://www.ancala.info recommended the new Paramo Men's Velez Adventure Light Smock. During my visit to the Lake District in October, I bought one, and have never used any other jacket since!
Unlike most other garments which use GoreTex, Sympatex, Teflon or other waterproofing linings, which wear out after a couple of years and then become useless, Paramo uses ANALOGY WATERPROOF by NIKWAX. This enables one not only to wash the garments in the washing machine, but to waterproof it at the same time.
Paramo have different thicknesses, but for me the Light Smock proved to be ideal. Even in temperatures of -18 degrees Celcius, which we had already this winter, I was never cold with the jacket using Icebreaker Merino, another superb product, as base and medium layers. If it gets really bitterly cold, one can easily wear a down waist coat underneath.
Being able to pack it small and put it in a rucksack makes it my favourite jacket, which travels everywhere with me, and makes it an ideal companion for snow sport. I have had every opportunity to test it this month!
http://www.paramo.co.uk