In reply to Mr Trebus:
Thanks, but it's not for portability, it's for office use. The ergonomic chair I have in here has armrests which are great, but they mean my right arm is extended too far to the side for 'general mouse-work' with a central, regular width keyboard. Witha narrower one, my arm will be in a better position...I hope! I'm currently getting a very sore right shoulder after an hour's work.
I'd have thought they were much of a muchness too, but the reviews seem to suggest otherwise.