The Advantage is certainly an investment, but I found it worthwhile. They last for eons, they're built like a tank. If you have significant wrist problems you might be able to talk your employer into paying for one, I know a couple people who have done that.

The Natural keyboards are good, but IMO the Kinesis is a worthwhile upgrade for the mechanical switches, programmability and durability.

The Kinesis keyboards are actually heavily inspired by an even more expensive keyboard called the Maltron. http://www.maltron.com/store/p21/Maltron_L89_dual_hand_fully...