In the last couple of months I have been buying some new walking/climbing gear. Quite a bit of my outdoor clothing is getting rather battered and worn out (a bit like me). In the past I have used a tee shirt/fleece/Goretex jacket layering system.
For cold weather I have a complete Buffalo system, which was very kindly given to me by Hamish Hamilton about 20 years ago. For cold snowy conditions e.g. Scotland/Alps this is excellent and I am sure that it will last a few more years yet. However, once the temperature gets above freezing it's far too hot, even with maximum venting.
In the last couple of months I have bought a couple of Paramo tops, which keep my nice and warm when I am walking or cycling. However, if it's very windy, or when I stop for a while I need something to put over the top. I do have a Buffalo belay jacket, but that's far too warm and bulky. In the past I have packed a fleece jacket in my sack, but even that was relatively heavy and bulky.
A couple of weeks ago I noticed a Rab Generator Smock in the sale at Joe Brown's in Llanberis. This has a Pertex Quantum inner and outer with Primaloft 1 fill. Primaloft is a man made fibre, similar to down. However, unlike down it doesn't transform itself into a soggy lump when it gets damp. The smock weighs around 330 grammes and packs up into its own chest pocket, so I am happy to carry it with me all the time.
I gave in to temptation and bought one. I am very glad that I did.