This is a question that I am asked all of the time. I do warranties for a number of different companies, but they all define warranty the same way: A defect of worksmanship or quality.
When it comes to warranties, I am on your side. I like doing warranty work, and if you have a warranty issue I will fight for you to get it covered.
Things NOT covered by warranty: Abuse, if you hit a large rock with your mower and bend the blade or break a spindle, that is not a defect by the manufacturer. Leaving old fuel in and having a gummed up or damaged carburetor is also not a defect by the manufacturer. This is the biggest one that I see, carburetor problems are almost always caused by old fuel and are not covered by any manufacturer.
I will take your of your problems whether or not it is covered by warranty, and I will always take the time to explain anything that you want to know about.
Update 2020. For a number of reason I've dropped Kohler. At current I am only doing warranty work for MTD / Cub Cadet and Generac / DR.