They are very different ergonomically. A good friend of mine swears by it, but for me it was very uncomfortable. I have pretty broad shoulders, so my typing position in a MS split keyboard is very comfortable. The Kinesis wants my hands aligned with each other at a set distance. To do that I have to bend my wrists outward a whole lot, so they actually hurt after enough typing.
It'd make more sense to me if the keyboard was actually split in half, so that I can have the two wells be as far or as close from each other as I see fit, but as it is, the Kinesis is actually worse for my wrists than even a laptop keyboard.
No experience with it, but I also fail to see why they need what looks like 750g of dead weight plastic just to hold the two sides rigidly parallel to each other. I thought their whole point was to have the keyboard conform to your body? I could also see wanting to put a trackpad or the like in between the halves.
The Kinesis wants my hands aligned with each other at a set distance.
I just looked at my wrists and hands on my Kinesis. While, yes, the keys are aligned along a single axis[1], my wrists don't bend at all. It's not like you have to align your wrists with the keys, your fingers do the aligning.
[1] for the inner keys on each side. The outer columns are dropped down to accommodate the shorty pinky finger.
It'd make more sense to me if the keyboard was actually split in half, so that I can have the two wells be as far or as close from each other as I see fit, but as it is, the Kinesis is actually worse for my wrists than even a laptop keyboard.