Hi Richard
Yeah I have had the sonic seam for a few months now. I really like it...but....
I havent really had it on in any really bad weather. I have worn it on cold clear crisp days with layers underneath and it has been fine. I kept my Greys jacket for spring/winter fishing as its a bit more substantial. The orvis is very light weight.
I bought it for the same reason as you. summer days/evenings when you dont really need a jacket but carry one anyway just in case. I think it will be brillant for this.
I am very happy with it but wouldn't like to be stuck in a big wind in Feb on the Dee with it. I also met a guy on the Stinchar at the back end last year who had ordered one and sent it straight back. He thought it was s**t but I think he wanted it to replace his everyday wading kit.
With my reviewers hat on I would give it 9/10 for what it is meant for. Zips are sturdy and waterproof plus it looks cool as f**k!! haha
Hope this helps.
Tight lines
Paul