I recently commented in another thread about performance problems with GDR2 - I have only had my HTC 8x for two weeks (unlocked c620e, USA with AT&T). The phone notified me of the GDR2 update last week and I proceeded to install it. I received the following three updates:
Microsoft Update 8.0.10327.77
Microsoft Update 8.0.10322.71
HTC Update for Windows Phone
When I first received the phone, other updates installed, but I did not note which ones they were. I noticed that WP8 lagged occasionally when first using the phone -- basic OS visual renditions of clicking on a link in the People HUB, clicking on tiles, the visual effect of an email being sent, etc. With the GDR2 update, laggy behavior is common. So in addition to two hard freezes after the update which required power button resets, overall the performance of the phone is less smooth than the Samsung Focus WP7.5 which I used for almost two years and had no visual effects issues.
Not sure which one of the recent updates did it, if it is unique to the 8x or even just my phone. But as a WP user coming from 7.5 to 8, I am disappointed with the OS performance and concerned if the problem will be solved.