I used to purchase my tickets using middle and last name, and only got static twice in 4 years: once by an UA agent and once at the Nexus checkpoint in YYZ. The CBP agent was far more understanding than the UA agent
I eventually switched over to First Middle Last, so I can transfer points between my Amex cards and Aeroplan. (Credit bureaus/card issuers get even more prickly than UA agents if your names don't match)