Google has created an entirely new Adwords API (v2009) that, if you're a developer, is going to rock your socks off. 

Google has created new web services for managing campaign targeting options and campaign-level criteria. All Web services share a consistent, data-centric interface with two operations (get and mutate). In addition, a secure authentication token replaces the login credentials required in v13 request headers.

The following table shows side-by-side differences between the web services provided in v13 and v2009.

AdWords API v2009 does not currently provide web services outside the scope of campaign data management. Utility services (ReportService, InfoService, AccountService, etc.) will be added in an upcoming release. Until then, continue using v13's utility services alongside v2009's campaign data management services.