Pros:USB, many function keys, lights for several functions
Cons:Poor quality switches-i.e. keys quit, not much life even in light use
The Bottom Line: Split keyboard, one of the few still sold. Switches apparently not the best quality, you may get about 18 months of service with a few hours per day usage.
I also like the natural key layout, I believe it's easier on the hands. I've had two of these in the last couple of years, they're fine while they last but when the keys start to drop out all you can do is toss it. Fortunately one of my favorite online stores carries these "white box" with no extra junk and a oem price. I would not again pay over fifty bucks for this but 25.00 is acceptable even if I know it won't last more than a year and a half. Microsoft certainly knows by now that these don't last long but it's still a current product, planned obsolescence still rules apparently.
When my latest one died (enter key quit suddenly) I pulled out my old natural keyboard pro (love that keyboard) and it fired up immediately. I like it so much afraid to use it too much since I don't think I can replace it anymore.
The 4000 does not have usb ports on it like some earlier keyboards did. It has media controls and the buttons across the top have extra functions as controlled by the Fn key.
In the box you get the keyboard a hand rest and a disk with the control software that microsoft provides (lets you change keys and if using a bluetooth setup gets that working for you).
To close: While it works it's a great keyboard but better buy two at a time because it just fails one day, no warning. I don't know if there's any way to fix the bad keyswitch I'd kinda doubt MS would provide a product that good...they want to sell you another. The keys are a touch mushy but nothing you can't get used to. Not bad just be sure you know it isn't going to last a real long time.