Installed it on my European 8X earlier today, and it feels quicker and smoother. It’s well worth it.
This is what Microsoft says about Update 3 (as the GDR3 update is called)
OS version: 8.0.10501.127 or 8.0.10512.142*
Accessibility. We’ve made several improvements for customers who are visually impaired.
Storage. Now you can easily free up storage space on your phone and manage temporary files. New categories show what’s taking up space.
Driving Mode. Feeling distracted behind the wheel? Driving Mode allows you to minimize incoming calls and text messages to help you focus on the road.
Screen. Reading emails in bed? You can lock your screen orientation so it doesn’t shift when you move your phone around.
Wi-Fi. Start preserving cellular data on your phone right out of the box—you can now connect to Wi-Fi during set up.
Internet sharing. Now you can use your phone’s cellular data connection from your Microsoft Windows 8.1 devices by pairing them over Bluetooth.
Bluetooth. Several fixes were made to address known issues, and improvements were made to connection quality for Bluetooth accessories.
Ringtones. Do more with ringtones now. Assign ringtones for text messages, so you’ll know who’s texting you without even looking. Use your custom ringtones for more things—text messages, instant messages, emails, voicemail, and reminders.
App switcher. Don’t look back. Now you can use the App switcher to quickly close apps when you’re finished with them.
What Droider thinks and found that Microsoft didn’t write
This is a nice update, and that you now can charge phone with it being turned OFF is a pretty big thing. As a friend said “How very 21st century of them”, and it was way overdue really. But, now windows phone 8 is getting somewhere. It’s getting better, but it still needs a GDR4 and a GDR5 and soon if they want to to keep up with Google and their Android.