There's no real point to this post, unless folks want to discuss what the problem might have been...
Up until last night, I had this faucet in my kitchen:
Getting warm water was a pain, because you had to go almost all the way to hot and then you started losing pressure.
I called Kohler and they sent me new cartridge. It didn't help, so I tried a few things. I swapped the hot and cold inlet tubes and the problem moved to the cold side - in fact it was even worse. That told me that the problem was in the faucet, not my plumbing.
I pulled the cartridge and, leaving the inlet tubes hanging over a pot, I poured water down into the body hoping to flush something out of the tubes. I saw a little debris in the pot and hoped I'd cleared it.
No such luck. The problem was still there when I put it back together.
I replaced the faucet with a similar model from Delta (with a lifetime guarantee) and now get 7.5 second fill times from both hot and cold, and warm water when I center the handle.
I can only assume that there is something blocking the fill tube that didn't get flushed out. I may take it apart just to see.