In reply to alexm198:
> but in the past I've not bothered with waterproofs in the alps. If the weather looks bad, you don't tend to go out.
No, but sometimes you get caught out, or decide to head out to see if it will improve. The weather over the course of an Alpine day is not sufficiently predictable to exclude rain, not to mention the fact that it can be good one day but bad the next, e.g. on the descent.
> Maybe others with more experience might think differently.
I certainly do - overtrousers are very useful indeed, not just to avoid rain (which you can certainly get on occasion quite high up), but also very importantly as a wind-stopping layer. Make sure if at all possible you have ones that will go on over crampons.