It is actually the latest keyboard as the link you sent is. Interestingly enough, I had another Comfort Duo and the back button stopped working. Logitech sent me that as a warranty replacement.
Even more interesting is that I have another identical Comfort Duo which is older than the one that "broke" and it's still running fine...my first Logitech wireless is also working fine (probably 5-7 years old now!)
I absolutely love that keyboard and mouse. The mouse has more buttons than I can even use. Unfortunately, the wheel tilts, scrolls, and is a button. The reason I say unfortunately is because the button almost never works right. I almost always tilt it sideways instead of pushing it. So, I just mapped the button to nothing and everything works great. Here is my "ultimate" configuration for the mouse.
Left Button: left button
Right Button: right button
Middle Button: NOTHING
Wheel Tilt Left: Browser Back
Wheel Tilt Right: Browser Forward
Zoom Buttons-------------
+: Ctrl + T for new tab in Firefox
-: Ctrl + W closes tab and many applications
100%: Middle button substitute
Thumb Buttons------------
First: Ctrl + Tab to cycle through Firefox tabs to the right
Second: Ctrl + Shift + Tab to cycle through Firefox tabs to the left
I just now realized I should change the Second Thumb Button to something else because I can always get to a certain tab by just going all the way around the "circle of tabs"
Anyway, this seems to work perfectly. Another great feature is that the keyboard, instead of trying to guess what programs you like, just uses numbers if I'm not mistaken (I'm not at home now). So I program 1= Firefox, 2= Thunderbird, 3= Media Center (duh), 4= Photo application
For some crazy reason, the media buttons don't always seem to work correctly and I haven't figured this out yet. With two monitors, I usually see MC anyway and can just click what I want but those buttons are handy. I'll have to keep checking that out. They seem to always work when MC is in focus but that isn't even very helpful.
Addition: I forgot the calculator button. It is so dang useful I can't believe it. How many times do I need to calculate a simple calculation and end up having to dig all the way to Accessories, blah, blah. And I often open two or three calcs at once. I love this button. I used to make it Microsoft Money but now I don't think it can be customized...it's the calculator.
When I got my first ergonomic keyboard it looked crazy and really strange. It looks really thick and just plain strange. After a while, it looks completely normal and I can hardly tell the difference with typing now. I don't do huge huge amounts of typing each day so I don't seem to have problems but it does seem to type nicely.
One drawback is that it's a bit pricey. They always say the keyboard is SOOO important. Well, the monitor is SOOO important, too. And speakers are SOOO important if you listen to music (most do) and that means the soundcard is SOOO important, too, or you will get stressed from poor music quality. Don't forget the hard drive. If you're computer is slow you'll get stressed and get SOOO upset. That means the CPU is also SOOO important...and lots of ram is SOOO important. Everything in a computer is SOOO important.
But I guess I can spring for an $80 keyboard when I've got $1200 invested in LCDs.