This video shows the difference between the 17mm lens and the 12mm lens focus speeds on the ep3.
[ame=https://www.youtube.com/watch?v=OGjLFo6G58o&NR=1]YouTube - The Phoblographer tests the Olympus 17mm F/2.8 vs the 12mm F/2 on the EP3‏[/ame]
The 17mm is slower than the 12mm, but it appears much faster than my E-p1. Keep in mind I've seen some videos of focus speed with the MSC kit lens, and it appears just as fast as the 12mm. Since the 17mm isn't an MSC lens, it may not have the hardware speed as the others. Still an improvement.