In reply to climbin_chris:
The good thing about shells is that as you say you can vary what you wear depending on the conditions.
This year I'm going to try...
a base layer, a thin fleece and a shell for good weather
and,
a base layer, a primaloft jacket and a shell for bad weather.
I seem to guess wrong most of the time though so I've taken to carrying a thin fleece in my rucksack incase I'm cold. The fleece in question is quite cheap so I sometimes leave it tied to a convenient fence in a stuff sack with my sandwiches - I don't really like skiing with anything but a very small rucksack if I can help it.
Above advice is based on my experience of Europe and Scotland, people say that America and Canada can be colder.