Installed the update and Dream Pack 2 last night.
Whoa... Big whoa. Like... Keanu Reeves in every movie he was ever in, "Whoa".
Can't put my finger on exactly some analytical angle of what is different with the physics and tires, but I'd bet that some of that listed above would explain it. Either the 64bit, new tire model, or something else has really made everything feel even better, if that was even possible (apparently, it
was).
After spewing goo all over barcelona with the new lambo and the RWD RUF (some of the new content), I then took out the Elise SC with a bunch of AI at Nordschlief (release car and Dream Pack 1 track), and probabnly had the best sim driving experience of my life. (That same statement, more or less, is also on one of the previous pages in this thread, which goes to show that saying it again must mean something entirely new.)
The AI is still stupid at times, but mostly just when braking for turns too early or being too cautious. I took that as a sign that I needed to turn up the AI smarts a few notches, and it did make things a lot better.
Anyway...
Get this game and/or get this update, if you don't completely hate yourself 
This is the game you've been looking for
