5.320 includes: 

The new Contour Mode has been added.  This Mode is part of the SI Enhance Menu in the Express Sonar Menu.

Contour Off shows you the standard Side Imaging view   

 Contour On removes the water column and shows you a flat representation of the bottom. 

Here is a brief video on this topic.  

Addition of Side Imaging range lines 

Side Imaging Navigation - When you are Navigating (GOTO) to a waypoint the boat icon on the top of the side imaging screen will try to show you the direction to the waypoint. This icon will move around to provide the direction to the waypoint. 

Addition of Down Imaging™ Zoom 

plus a fix relating to DownImaging bottom lock, DownImaging shallow water depth detection, DownImaging sonar recording/playback at shallow depths

If you have a: 

5.320 includes: 

Resolution to Interlink issues affecting GPS connectivity and waypoint sharing, along with changes to:  importing from an MMC card, setup menu options, exit during remote sync in progress, GPS Course and auxillary temp alarm.  A new feature was added called Interlink Erase.  This allows you to erase all information on the Interlink without affecting GPS information on your units.  Both units connected through the Interlink must have 5.210 software or higher loaded onto their units for these changes to work.   

Interlink Erase can be found under the Interlink menu option on the Accessories tab. 

Scroll down to Interlink and right click

Confirm - Yes is a right click

The Second Confirmation is also a right click

You will then get a message that the Interlink has disconnected.

Then you will be asked how you want to participate

and then you will be asked what data to keep. 

Chart layers were added, custom chart menu display was fixed along with minor Downrigger fixes were made for those with Cannonlink.

If you have a: 

The Auxillary Temperature information box was added.