I got one of Geoffs lock bars. I think intial turn in became slightly duller and low speed turning was slightly heavier - but honestly the difference was negligable. Plus, I've had it on there for long enough now that I'm used to it and prefer it this way.
The main improvement for me was a long sweeping bends and high-ish speeds. Before with HICAS, the arse-end would wiggle around at unpredicatable times. A lot more stable now...