The Nokia Conversations Blog has now posted an (apparently official) comment on PR1.3:

http://conversations.nokia.com/2012/...-update-pr1-3/

Quoting from the article:

The main improvements include:

• Mail for Exchange (MfE) now supports client certificates.
• Localisation improvements and support for new error codes with the Facebook app.
• Twitter API changes that reflect the back end infrastructure of Twitter.

As well as these main updates, there are also some general updates.

• AccuWeather widget weather update fixed.
• VoIP calls now work via Skype/Gtalk when in flight mode and connected to WLAN.
• Changing the “week starts on” date within the calendar error now fixed.

There are also a lot of small improvements on network and connectivity performance.