The release is in line with earlier speculation that the company planned to dole out betas in two-week cycles.
The new version includes some general performance improvements and fixes a number of issues that had cropped up in the second beta, including problems with iCloud, AirPlay, and the Messages application.
The user interface received a few tweaks as well, including more transparent folders, redesigned music controls, and the calendar now shows which days you have events on. The update also brought with it enhancements to FaceTime and a better Siri voice.
It's standard practice for Apple to release several beta versions of the software before it debuts it to the public. Apple has said iOS 7 will come to the public in the fall. iOS 6 had four different beta versions between its June debut and late September release last year, so we can expect at least one more beta to arrive for iOS 7.