The update will be pretty much the same as the one BlackBerry had pushed out earlier. It will weigh in around 475MB in size so you might want to hook onto a WiFi network before downloading. The update will bring about several changes and improvements to the phone, like an improved camera where it has been retuned for better low-light photography.
BlackBerry has also improved upon the battery by tweaking the software so in theory you should be able to squeeze out a bit more battery life. Changes made to the system has also made it more stable and reliable, and according to BlackBerry should reduce instances where it crashes or freezes.
Last but not least, as BlackBerry had promised, they have released December’s security patches so that your phone will stay secure even against the latest Android security threats, so if you haven’t updated your handset yet, keep an eye out for it.