I have one of those Paramo gilets and I think it is almost my favourite garment. It weighs nothing, packs up into it's own pocket and goes everywhere with me all winter, (and quite often in the summer as well) on a bad day I even wear it round the house. It's perfect when you stop for a sandwich on a cold day, you just sling it over your jacket to stop you losing heat. It's a lightweight extra layer whenever you need one, and though it isn't waterproof it still insulates when wet.
When I bought it I thought it was an expensive luxury and hoped it would be useful. But, as I say, it is about my best bit of gear. I feel the cold, and suffer from Reynauds, and on many days it has made the difference between a good day out and misery. In fact often the difference between a good day out and staying home with a book.
But then I do live in the cold North.