I suffered from some form of CTS and I can say split keyboards didn't really make much of a difference. It's all about placement of the wrists and keeping a good posture. Also breaks, lots of small breaks throughout the day.
A properly designed split keyboard is aimed at improving the placement of the wrists though.
I found a minor but noticeable benefit many years ago switching to the Kinesis Advantage. I've recently switched to the Truly Ergonomic keyboard; I've yet to decide if it's better or worse overall than the Kinesis.
