I read some of the docs and changelogs to double check some of the new features.
1.As for iOS10, this is what Chartboost says why is it important to upgrade:
As part of iOS 10, Apple is introducing major changes to its Limit Ad Tracking privacy option. These changes impact ad serving across all mobile games running iOS 10. Users that choose to turn on Limit Ad Tracking will affect any developer using a non-iOS 10 compatible SDK by limiting control over the number of ads shown per user. Further, users with Limit Ad Tracking enabled restricts proper attribution of installs that you deliver to advertisers, potentially lowering eCPM. You can ensure that your Chartboost integration continues to run smoothly by upgrading to iOS SDK 6.5.
2. I only found some info about animated gifts support.
It matters a lot for advertisers, as for publishers, it should work out of the box on interstitials, form Chartboost:
Publishers, elevate the player experience
To elevate your player experience with animated GIFs, upgrade to the newest SDK 6.5 for the full benefits. Your interstitial publishing campaigns will now include animated GIFs, no need to update anything in your dashboard.
Wen you try to create a new advert campaign as a advertiser, there is a new option indeed, for animated gifts.
I couldn’t find anything for playable ads, not sure what changed here, if any.
But there is some small info in 6.5 changelog.
3. I found something interesting in changelog for 6.4.2 Android:
Publishers only: All Chartboost ads are now shown using CBImpressionActivity. You must add CBImpressionActivity to your AndroidManifest.xml file, like this:
Note: Make sure hardware acceleration is added and enabled when declaring the CBImpressionActivity in the manifest.
Not sure if this is already done or not.
4. Also there is a note for 6.6 and iOS
This library is built using Xcode 8 with bitcode enabled. In order to use it with prior versions of Xcode (including 7.3.1), bitcode must be disabled.
Anyway, probably you already have seen some of this.
That is all I found for now that can be interesting.