Lenstip.com has a review of this popular Distagon 25/2.0.
This lens has a respectable speed in a rather good weight/size package, it is loved by many for this reason.
Other than its superb build quality, lenstip.com reports that it has very good longitudinal CA (bokeh fringing), which is hard to achieve for fast wide angles, but this Zeiss Distagon 25/2.0 does it well.
Its floating element design assures sharpness at all focusing distance. The distortion is pretty decent too.
Take a look at the full review at http://www.lenstip.com/index.php?test=obiektywu&test_ob=331