I originally purchased this keyboard back when they were introduced - I want to say 2008... Just got my 2nd one on February 9th, 2012.
I couldn't care less about the back-lit keys (but I'll admit, they're pretty great in low light conditions), I love the keyboard for it's almost identical-to-laptop key feel. The keys are very slim (whole keyboard is insanely slim) and very quiet. A person could be sleeping in the same room and not be annoyed too much by keyboard clicks.
The only issue I ever had was that the super-tiny tabs holding on the keys broke on the Left Shift key. I should have taken advantage of the 3 year warranty back then and gotten a replacement but I put up with it since it was only half-broken. Instead, it became a habit to play with the loose key - like a kid plays with a loose tooth. Just recently though, the key completely broke off. Unfortunately, I was now outside of the warranty.
I've had experience with many other keyboards over the years (my other machine and at work) including the Logitech Wave, Logitech Comfort (the split one), MS Comfort Curve, MS Ergonomic 4000, MS Wireless 7000, and the MS Arc (a great keyboard, but low build quality and no number pad) to name a few. This is the only one I've purchased twice. Great keyboard. No complaints.
If they were the same, I would have opted for the wireless version, but it's a completely different keyboard.
Also, I must praise Amazon for their speedy delivery. Even with the free shipping, I got the keyboard a mere 2 days after purchasing it.