For the most part I have had good luck as a dealer with companies honoring their warranties, providing that you follow the guidelines to a T, and not try to claim warranty on things that are clearly not warranty, and especially for items that are specifically called out as not being covered, such as blades, belts, tires, battery, seat, stale, contaminated fuel, etc.
Also be aware that the mower OEM doesn't cover the engine or the drives, they will have their own warranty through that manufacturer, such as Hydrogear, Briggs, Kohler Kawasaki.