I've been using my new Kinesis Freestyle keyboard all this afternoon.
Check out my Flickr set for some pictures of it in action, as well as some closeups of the issues I'll mention below.
Long Story Short
I can get past the few slight issues, and I love it.
I'm no keyboard connoisseur, but I know what I like, and I like the switches on the Freestyle. The keys have just enough travel and resistance to suit my tastes. They feel good, and make a pleasing sound. I don't think they're mechanical switches, but I can live with that.
The Top Function Keys
The top row of F-keys doubles as your standard Mac modifier keys, using a layout very similar to current Apple models. They've added a button that toggles Dock auto-hiding, which is neat if not useful, and a power button.
I normally hate function-keys-cum-media-keys -- I like to be able to adjust my volume, play my media, and hit function keys when I need them, without using a modifier key. Kinesis thought of me when making this keyboard: the fn key (which toggles between F1-F12 and Apple shortcut keys) isn't a modifier, it's a mode-switcher (like caps lock). When I'm in need of full F1-F12 love, I hit that key and I've got it. Otherwise, I leave it off and have my media keys and so on. I can't say how much I appreciate that.
The Driverless Hotkeys
There are some hotkeys on the left-hand side which appear to be hardware macros. Internet back/forward, beginning/end of line, cut, copy, paste, undo, select all, and the aforementioned "fn" key.
I can't see becoming dependent on them, but they're handy if you remember to use them.
If you're coming from a regular Ergonomic keyboard (I previously used the Microsoft Natural Elite 4000), the location of the left command key is weird: it's positioned (below) halfway between "x" and "z" instead of directly under "x". I constantly miss it.
Same with the right Shift key: there's padding between it and the up-arrow, and I sometimes shove my finger there instead of hitting the Shift.
Since it's a compact keyboard, you don't get the pageup/pagedown/home/end/insert/delete block. There's no insert key (which is fine), delete is above the backspace key (and just as wide), and the other four keys are vertically aligned on the right-hand side of the keyboard. Not the best layout, but given the constraints, not the worst.
The Last Word
I've got mine at the Innova office right now, and I'm strongly considering buying one for home.