CreativeService: The API now supports the skippableAdType attribute on VideoCreatives and the mezzanineFile asset on VideoRedirectCreatives.
CreativeWrapperService: The HTML header and footer fields have been renamed to htmlHeader and htmlFooter, and they are now strings instead of CreativeWrapperHtmlSnippets.
ProposalService: Proposals are now automatically synced with marketplace. Therefore, the proposal action SyncProposalsWithMarketplace has been removed (sending this action with performProposalAction is now a no-op in previous API versions).
PublisherQueryLanguageService: In v201702 the Change_History table was introduced. Now, new entities for Sales Management have been added to the EntityType column. The new entities are
ReportService: DateRangeType now supports a new LAST_3_MONTHS option. Also, several deprecated reporting metrics have been removed. They can be replaced with their corresponding partner management metrics, so you will need to update any code using those fields. For more information, check out the support entry for partner management reporting metrics.
For a full list of API changes in v201708, see the release notes.
With each new release comes a new deprecation. If you're using v201611 or earlier, it's time to look into upgrading. Also, remember that v201608 will be sunset at the end of August 2017.
As always, if you have any questions, feel free to reach out to us on the DFP API forums or the Ads Developer Google+ page.