Well, I tried to touch type at my typical speed (which is already gonna be weird seeing as how I typically use an ergonomic keyboard), and while I like the way the keys click, not having that concave surface causes exactly the problem I suspected. You can't easily feel your way around or know how centered your impact is on the keys.
I'm all for pretty, especially when it comes to Apple, but let's not go back to an Atari 400 keyboard.
I as well use an ergonomic keyboard and have not spent a lot of time with the flat keyboard that comes with the iMac... but I didn't find it that bad. Isn't it supposed to be just like the integrated laptop keyboards? The real test will be when my wife really begins to use her computer.