Haven't seen any major changes with this update, but a little smoother and no stuttering or freezing. I also think the Bluetooth audio pickup in my car on phone calls is better, which, if it holds, will be much appreciated. I had a few instances where the call wouldn't hang up in the car. But I didn't see this on the ride back.
I installed it yesterday afternoon and experienced a bug in the morning that had recently cropped up, where my emails weren't displaying properly. They would be listed in the inbox but when you tried to open them only the header text would display, with the body of the email in blank, Refresh would bring down new emails to the device, but with the same blank condition. A soft reset fixed the problem. I will give it a day or two to see if this settles away.
I took about an hour and a half ride this afternoon with Scout GPS Navigator running, and with the 1520 plugged into the car charger and it still lost charge steadily and ran hot after I got out of the car.
When I've updated my Blackberry with a beta or leak, there was usually a breaking in period of about a day after which the OS would become noticeably smoother, quicker and more stable (at least for the good builds). I think there was some actual technical reasons that this was true, and not just my subjective delusion. I don't know if an update like this on WP has a similar breaking in period though, but my sense is that it does.