Being able to target users by OS (Operating System) is one of the many new features recently launched within AdWords and allows marketers to control their mobile advertising dollars. As mobile commerce comes to the forefront this as well as many of the new updates will assist advertisers in focusing on the proper devices and users.
OS Version Targeting
First off, being able to target your spend toward iOS, Android, WebOS or others (as well as versions) is particuarly important to app and game developers who want to be certain they are not wasting spend on someone who can't even use thier product. Conversions are also key in this segmentation as many OS's will convert better than others.
Now AdWords can detect the signal strength of the mobile user to, again, see if it is worthy of serving up the advertisement. If a user is on a slow connection then there is less likelyhood the ad will serve. Why waste spend when the user can't convert.
Google announced these updates and confirmed it is crawling mobile sites, so now is as good a time as any to create a mobile version of your site and focus on page load time. These are key pieces with the popularity of tablets and mobile devices.