Here's the Verizon info sheet on the update...looks to be pretty much GDR3 features...nothing beyond that(?) seemingly from Verizon.
http://support.verizonwireless.com/dam/support/pdf/system_update/windows-8x.pdf
------------------------
Software Update for the
WINDOWS PHONE 8X BY HTC
Software Version 3030.0.41301.605 ; Baseband: 0.17.50.0918_3.
Verizon Wireless is pleased to announce a software update designed to improve the performance of your Windows
Phone 8X by HTC smartphone.
KEY DEVICE ENHANCEMENTS
Data Usage Applies. ? 2013 Verizon Wireless. 1013-G7885
Windows Phone 8X
by HTC
? Choose whether or not to receive call and text notifications while in Driving Mode
? Added ability to read aloud information on your phone calls, send text messages,
and more with enhanced support for Mobile Accessibility*
? BING applications are now supported (includes BING Finance, News, Sports
and Weather)
-App comes preloaded for new users
-App is accessible for download via Windows Phone Store for existing users
? Multitasking capabilities have been enhanced
-Press and hold the back key to open a list of recently accessed apps
-Select an app to reopen it, and tap the X to close it
? Lock screen to portrait or landscape layout with Screen Orientation Lock
-------------------------------------------
HTC hasn't put up any support info on GDR3 and is still stuck at GDR2 info release....at least that I could find.