That's funny, I just got a replacement for my G15 (blue one) a few days ago. The backlight for the little screen stopped working (apparently although the screen opens and closes, if you do it too often like I did something comes loose all by itself). They sent me the updated (orange) one for the low, low price of the $15 shipping of the original keyboard to them.
Just so you know, they won't care about you having a receipt or not, which is a relief b/c the G15 (including the new one) has an abysmally short warranty of only 1 year, compared to the 5 years most of their other ones have. Also it takes them a while to do anything like any warranty situation, so if you want a new one, act quickly.
If you do go the route of getting the new G15 and you have the older version, boy are you in for a treat. Nice as hell, typing feels better, plus each key is coated with something awesome and rubbery. Also, although the blue of the old one matched all my computery shit real nice, the orange backlighting of the new one is way easier to see. The screen is a bit smaller, though, but at least it's also orange. All in all the new G15 rocks.
I'm thinking of stocking up on them in case logitech decides to replace them with something fatally flawed like the mx518 (no forward button on the g5/g7? honestly...?). I'm also considering switching out all the orange LEDs for blue ones, but I'm not brave enough b/c i don't wanna mess with the screen.
Well, I went on a few tangents, but hope it helps.