Yes I've noticed on fares to just about anywhere from Florida. Within 2-3 weeks they tend to equalize with the competition, but advance purchases are much higher.
Example of a few of my recent searches: FLL-SEA early June, Friday departure Sunday return, NON-redeye: UA = 373, US = 712.
Same criteria different weekend in June, FLL-LAX - UA 363, Spirit 168, US 533.
I've flown UA more in the past year. It's not so bad in coach. I have been able to score some decent UA codeshare fares on US metal - so check that out too.