Well I have found one change ..... when I pushed the volume up to full I got a warning saying it could damage my hearing if using headphones etc .......... It just appeared the once and I can't replicate it ! I am sure that the update was more than just that !!!!
FYI my firmware revision is now 1532.20.2004.206
Messaging improvements. A great messaging experience is now even better. You can now add multiple recipients at the same time when you send a text message and automatically save unsent text messages as drafts. You can even edit received text messages before you forward them.
- Text replies to incoming calls. Can?t take a call? Now you can send a prewritten text reply to a caller directly from the call answer screen. It?s a nice way to let people know that you?re not ignoring them.
- Internet Explorer improvements. You can now change your settings to prevent pictures from downloading automatically?an easy way to help keep data usage low. You can also delete selected sites from your browsing history and leave the rest intact.
- Wi-Fi connectivity. Got a favorite Wi-Fi network? Windows Phone 8 will now prioritize Wi-Fi connections based on your connection history.
Rogers HTC 8X users reporting OS update now available, fixes messaging issues | MobileSyrup.com
Looks like the Portico update perhaps?