I own a straight and a curved JP 043. They both play very sweetly and are unarguably great value for £325 or whatever they were. I bought the curved last Summer, and the straight in November.
My "proper" soprano is a Yanagisawa Elimona - and these Packers are copies of modern Yanis. Are the rods and keys as beautifully machined as a Yani? No - but they are still pretty well put together. Are they as nicely finished? No - but they are very decently finished. My curved sop does have a little evidence of uneven lacquer in a couple of spots - but you do have to look for it.
I've not done a side by side comparison with another curved sop, but on it's own merits it plays in tune and with a warm sound. My straight JP plays with an amazingly broad tone compared to the majority of sops I've played - and I've played just about all the modern big-brand sops going.
Having said that, I have found that on both saxes that I've had to tighten a few screws from time to time. A minor irritation.
So, as far as curved sops go, my own impression is that it would be very hard to beat the John Packer - for the money, that is. Bauhaus's curved one is probably worth looking at - but it's already significantly more expensive.
It comes in an OK case. The straight came in a much better case.