Kohler has been fantastic with warranty repairs. We replaced our kitchen faucet with a pull out spray/stream Kohler in '07. In the intervening 12 years they've replaced the screw on spray/stream end twice (it gets clogged over time and there's no way to clean it), and sent us a new hose too, all under warranty - I emailed them with a description of the problem, and the new part was sent within a day.
We also have Hansgrohe in our master bath. They've replaced the pop up sink drains with a new style after one of the originals failed, and the shower handle was also replaced under warranty.
As for Moen, the original builder grade stuff, installed in '88 in our powder room and guest bath, have never caused any problems. Hmmm...