Cheers everyone. Like most other people I've read a lot about the shortfalls of this bike (as I do with any bike I buy). I'm just going to ride it as-is for a while and decide for myself what fixes I need regarding the rear shock and the twitchy throttle.
My biggest regret with motorbikes is selling my old Speed Triple (picture below) - among other reasons I was tired of the harsh shock, which like the GSXS had virtually no high speed damping. In retrospect I should have kept that bike, which I picked up for a bargain, instead of triggering a series of expensive bike changes. All the Speedy ever needed was less than $1,000 in a shock to be a near-perfect bike.
I'm hoping the GSXS lasts me a long time, which means I'm prepared to spend some money getting it just right. As far as I'm concerned, once you've chosen a style of bike, the engine becomes the most important factor. Anything else can be changed, to an extent, but you've gotta live with an engine. There are few bikes I'd chose ahead of the GSXS in terms of engine alone (only a Tuono 1100, and maybe a Superdule, but never ridden one).