ePhotozine posted their full review of this lens:
There is a lot to like about this lens. The fast maximum aperture is great for low light applications and for improving the ability to throw the background out of focus on the small MFT format. The constant f/1.7 aperture maintains these advantages right through the zoom range. In theory, it also would make calculations for manual flash simpler, but probably these days that is a relatively minor advantage for most of us. Focusing is virtually instantaneous and very, very accurate. The lens hood is too easy to release, but once aware we can watch for that.
Of course, the icing on the cake is the quality of the results, with the one exception of a possibility of flare. Overall though, a superb bit of kit and a lovely lens to complement the MFT system.
Leica DG 10-25mm f1.7 review so far (CameraLabs).
Panasonic Leica DG Vario-Summilux 10-25mm F1.7 ASPH Sample Images (Photographyblog).
Panasonic Lumix Leica 10-25mm f1.7 Objektiv, MFT ist nicht tot… die verrückte Linse im Praxistest (Krolop-gerst).