I bought a NIB G5 off craigslist a few years ago for $20. It was the single side button one and after a few months, the right button got really unreliable - I was playing COD4 a lot and it made the game unplayable.
I called them and they did have me send in my old one and then they shipped me a neat new 2 side button G5 with the blue crackle finish.
Great experience with their mice - however, I had a G15 v1 die about 14 months after I got it and it only had a 1 year warranty. Yeah, too bad about your $100 keyboard.
If they would offer a good warranty, I would buy their gaming keyboards again, but 1 year is insane - especially on the high end ones.
Anyway - I had a similar experience with one of the first gen MS Explorer Mice with the LEDs. They just shipped one right out, no questions asked.
The big names will probably take good care of you but if you bought a cheapy no name mouse, you should probably just replace it.