I have owned a number of Delta products and have been very satisfied.  In fact I have a bath faucet I installed 33 years ago and it is still working great.  HOWEVER, I bought this kitchen faucet 4+ years ago and from day 1 have had mixing issues.  One would expect a straight up movement would give a mix of hot and cold but very hot is more the norm.  A slight adjustment to the right produces cold, not lukewarm.  A slight adjustment to the left produces very hot water.  The more the valve is opened the cooler or less hot the water is.  Also, as of late, the faucet is dripping and it cannot be fixed simply by running hot water (to expand gaskets).  Love the design, but am considering replacing to keep my wife from constantly complaining.  If the dripping issue has a fix I would love to know what it is.  As for the temperature issue, I'm not sure there is a fix as I believe it is the design of the valve causing the problem but willing to listen to any ideas.