DxOMark published their review of the Leica APO-Summicron-SL 35mm f/2 ASPH lens (Adorama | B&H) – here is their conclusion:
Leica’s APO-Summicron-SL series appears to offer just that, and its smaller, lighter f/2 lenses are as well or better corrected than “standard” f/1.4 versions. With such an exotic optical construction, then, the Leica APO-Summicron-SL 35mm F2 ASPH has many attractive qualities, including good sharpness starting at f/2, low LCA, and almost no distortion. It’s also almost as bright as some f/1.8 lenses. All of this comes at price, though, and the $4595 ticket isn’t for the faint-hearted.
In this review, we have compared the Leica APO-Summicron-SL 35mm F2 ASPH mounted on a Panasonic Lumix DC-S1R to its closest rivals from other brands. Remember that the lenses are intended to be used on different camera systems and mounts, so the comparisons are not strictly applicable.
Additional information on the Leica APO-Summicron-SL 35mm f/2 ASPH lens can be found here:
Leica APO-Summicron-SL 35mm f/2 ASPH lens officially released
Via DxOMark