In less than a week, Apple's iOS 5 system upgrade has taken over a third of iOS devices. A mobile app analytics company called Localytics tracked device usage between Wednesday and Monday to find that 33 percent are running iOS 5 already.

The percentage reflects usage on all platforms including the iPhone, iPod Touch, and iPad. The next version iOS 5 rolled out last week with over 200 new features, apps, and upgrades. Some of which are most appealing to consumers are cloud-based storage syncing service iCloud and a notification central where all your updates come through. The new OS also integrates popular networking site Twitter and a new messaging center iMessage.

Every 4S phone is operating iOS 5, which prompted company Localytics to examine what platforms besides the iPhone 4S were running iOS 5. They found that usage is actually highest on the iPad 2 right now at a 36 percent, followed closely behind by the iPhone at a 35 percent.

Apple itself reported that 25 million users are running iOS 5, further showing how popular the OS has become. With the iPhone 4S selling over four million units in the first three days of its launch, the iOS 5 is sure to continue on this upward trajectory of conquering the OS territory.