I tried a Kinesis freestyle, but ended up returning it.
The adjustability is kinda cool, but I could never get it to be as comfortable as the MS natural elite. It has pretty good switches for being membrane.. better than the MS Natural Elite I'd say, but each half is like a half of a flat keyboard. No curve.
I've gotten used to the Alt being between X and C on my ms natural elite, and I've sort of found that it's very hard for me to move to any other kind of keyboard.