Not great, but good
I traded in my Pana-Leica 25mm D for the 25mm DG, solely for the size/bulk factor. The DG is a much, much better fit on a micro 4/3rds camera than the D was, being designed for the system. (The D is only at home on an SLR.) There was a serious difference in price between them as well, with the D clocking in at a hefty $1500 or so MSRP, while the DG was a more attractive $600. I was hoping that the price wasn't an indicator of quality, but I've been somewhat disappointed in that regard.
In a nutshell, the D was a far superior lens in every way except its size and focusing speed. The DG, in comparison, lacks the D's tack-sharp image quality wide open. I tend to avoid shooting at f1.4 now unless I absolutely can't help it. It performs well enough between 2.5 and 4, however. At around 3.5 it approaches the image quality I achieved with my D. As an added bonus, it has virtually no noticeable chromatic aberration, whereas the D had plenty.
My second complaint - and this is a BIG one - is the utterly horrific pincushion distortion. You won't notice it unless you shoot in RAW and are forced to correct it manually. (My Olympus EP-1 corrects it automatically in JPEG output.) I don't know how to quantify distortion, but I do know that the amount this lens produces should be flat-out unacceptable in any product with the Leica name on it. They built a reputation on lenses that provided beautifully accurate images, and this lens is simply not anywhere near that standard. I've seen cellphones that take less distorted pictures than this lens.
All told, I'm satisfied with the lens. I'm not excited by it and I'm occasionally frustrated by it - especially when I compare my recent photos with ones I took last year with the D - but for a frequent traveller like myself who needs portability above all else, it suffices.
Still, I REALLY wish they'd put some more work into it...
- Severe distortion
- Significant blur wide open