United has got to be the works airline in marketplace today.
14 flights flown in 2014. To recap
2 times my luggage was left in Chicago
2 flight cancellations (over 48 hours before they could rebook me)
7 delayed flights (6 out of Chicago) over 1 hour
2 requests to use miles for upgrade that they could not accomodate
The airline is awful and doesn't respect its customers. The frequent flier program isn't worth the hassle and strings attached.
Do youself a favor and look at Southwest, Delta or American.