Showed up at BOS in the evening, only to find the 5* section completely empty. PC had a lone Infiniti Q50 and Chrysler 300. Was about to snag the Q50 but then a Q70 with just under 20k miles pulled up, so I went for that.
BTW, I got PC through United, but it's been a few days and my account wasn't updated yet. The gate agent did inquire how I got that car as I was only 5* and asked if I wanted to pay to upgrade, but then she was able to make a call and let me through upon checking with the back office regarding the pending PC status.
I obviously got pretty lucky, but definitely happy with Hertz/PC/UC thus far!