I'm just now reading all the reviews as I'm on hold with customer service.  I have the same problem, the cold water faucet is extremely hard to turn.  Problem started about 5 months ago.  Faucet is about 4 years old.  I already received a new cartridge (under their free replacement) policy but it didn't fix the problem.  It looks like I'll have to request a new cold water handle and pray that I can fix it myself?? Product looks good, no complaints about customer service but still annoying to have to deal with it.