Took six months of waiting but they finally came in. Got my waiting tires mounted and balanced this morning, and then spent the next hour heaving heavy things around to put them on the car and store the old ones in the basement.
Went from 255/40R19 on 19x9 Front / 275/40R19 on 19x9.5 Rear (staggered oem wheel and tire setup) to 275/45R18 on 18x9.5s for all four corners.
Original tires are Michelin Pilot Sport 4S, new ones are Bridgestone Potenza S007A. I got a screaming closeout deal on them so saved a lot of money despite all the reviews saying they are roughly comparable in grip to the PS4Ss. Might not have quite as high a tread life though. We'll find out.
First road impressions: The bigger, meatier tires with taller sidewalls definitely have a bit more cush to them, and turn-in isn't as immediate or crisp. BUT the new tires soak up bumps better and maintain a better contact patch through broken pavement in corners, and provide objectively more grip at least in acceleration. Used to be I would spin the tires through 2nd gear and into 3rd. With the new Bridgestones, 2nd hooks immediately and stays hooked. I haven't pushed it suuper hard into corners yet so that's an unknown but I expect it will want to oversteer a little bit more because the fronts are wider than stock. I'll report back eventually to let you know how at-the-limit dry traction is in lateral loading, as well as wet traction.
Saved 6.5 lbs per front corner!
I haven't weighed the OEM rears yet but they're at least another 7-8 lbs over the fronts, so probably about 14 lbs of saved rotational/unsprung mass in each rear corner.