Regular keyboards give me a pain — a pain in the wrist, specifically. It makes a huge difference when you're typing a lot for emails, blog posts, proposals, articles ... and novels.
I tried a number of keyboards.
The Kinesis Advantage is one of the most radical ergonomic keyboards out there. With scooped-out keyboard forms, it's designed to conform to typical finger paths, not conventional keyboard grids. However, there's a very steep learning curve. What put me off, though, were the rather long keystrokes. This issue can be addressed somewhat with some hacks, such as swapping key switches and adding rubber rings underneath each key to try to limit they keystroke distance, but this already is a very expensive keyboard (several hundred dollars) and having to take it apart key by key just to make it acceptable didn't feel all that sensible, so I somewhat regretfully returned it.
The Microsoft Sculpt keyboard is a lightweight and modern offering from the company that had the most popular ergonomic keyboard in the 1990s. It wasn't bad, but the Option and Command keys are swapped in position, which would require new less-optimal keystroke habits. In the end, I sent it back primarily for this reason.
The Goldtouch Go!2 keyboard does not have curves, but it does have a universal joint in the middle that allows you to angle they left and right halves of the keyboard, and even peak it in the middle, so you can find your own comfort position to avoid things like wrist pronation that can contribute to RSI. I like the quick-action scissor-switch keys, which are most like the keys on Apple keyboards, and don't require a ton of motion in order to register a keystroke—very important when you don't want to feel like you're typing through mud. The keyboard has a switch for Mac and PC layouts. And it folds up, making it portable. Some people may dislike that it's a USB keyboard, but I don't mind—one less battery-driven device to worry about.