For me (usually 2 to 3 UAL flights a week), it's been a weirdly disproportionate full/emptiness.

On long haul domestic/cross country, regular economy is packed to the freaking gills, and Economy Plus less than 1/2 full.

On short haul, the flights are less full, and Economy+ is vacant.

Routinely now they have a senior gate agent come on board to try to upsell, usually after several people get pissed off after being told they can't move up to the nice empty seats up front without paying more.