A few months ago my G5 mouse started randomly changing dpi settings and then disconnecting from my computer. I called up Logitech support and I must say I was pleased with the experience:
1. Short phone menu. I had to go through only 3 options.
2. Short wait time. And by short, I mean as soon as I clicked the third option, I was immediately connected to a CSR.
3. CSR was polite.
4. Their warranty was amazing. For one thing, it lasts for three years instead of the usual two. Secondly, since the G5 is no longer produced, they upped me to the G500 which has a much better laser, dual-mode scroll wheel, heavier weights and an extra button on the side.
5. Overnight shipping+tracking
6. At no cost
I was actually really surprised with the service. Their web site doesn't say "zomg we're #1 in customer service ratings" or anything, and before this I had never actually gotten something out of a CSR regarding a warranty. She didn't try to squirm out of the warranty or anything.