I bought a Sept. 2013 110K is300h sport recently from Lexus Pre-Approved used - no warranty - exported to Ireland. The unexpected issues I encountered were: 1. worn tahara trim on driver seat (threadbare) - apparently quite common even in low milers - was aware when I bought 2. wipers working intermittently (disconnected the rain sensor - still stop in middle of screen) - uncommon problem - unaware when bought I replaced the trim (850 euros). I have yet to fix the wipers - I suspect its the switch on the console.
Matt, Did you ever resolve the window squeak? I have it too, just like you described, driver side, wet conditions. 2013 with over 100K on my clock so thinking its age related. Tried silicone spray to no avail. Cheers.