I bought the black version of the M.Zuiko 17mm F2.8 lens after selling my Panasonic 14mm F2.5.
While the Panasonic 14mm is an excellent lens, and I highly recommend it, I found it to be a bit too wide for my needs for street photography. When I want to shoot really wide, I shoot at 12mm with my M.Zuiko 12-50mm kit lens that came with my Olympus OM-D. I did consider getting the new M.Zuiko 17mm F1.8 as well as the new version of the Panasonic 20mm F1.7, but found them a bit to pricey for my needs, since I already own a Panasonic-Leica 25mm F1.4 lens. I did also consider the Sigma 19mm, but did not like the extra size.
The 35mm equivalent format is what's used in Fuji's X100S and the one favored by many enthusiasts. It is touted as the format that matches the field of view of the human eye. With its 34mm equivalent format, the M.Zuiko 17mm F2.8 hits the sweet spot in terms of format, speed (F2.8), sharpness and price. So for an affordable "one size fits all" wide pancake lens, I thought the M.Zuiko 17mm might just fit the bill!
I was indeed aware that the M.Zuiko 17mm F2.8 did not score too highly in the technical reviews, especially that the slight corner softness persists across all apertures, and that the chromatic aberration (CA) is easily noticeable along the edges in high-contrast scenes.
But where the rubber meets the road is in actual user experience, especially street photography.
It's small size, metal barrel and plastic manual focus ring make this lens a joy to handle. It easy to use in a discrete way. While auto focus is slower than on my M.Zuiko 12-50mm kit lens, it is accurate and fast enough for capturing spontaneous street pictures.
The lens is sharp wide open at F2.8. Corner softness is only slight and hardly noticeable in street or portrait photography, and barely noticeable in landscape photography. (In overall sharpness it beats both the M.Zuiko 14-42mm II and 12-50mm kit lenses at 17mm, although the Panasonic 14mm F2.5 is definitely sharper.) And, given that CA is easily corrected using any decent photography software, such as Lightroom or Apple's Aperture, it is not a major issue either. (My typical CA correction settings for this lens on Aperture are -0.56 for magenta/cyan, and -0.28 for purple/yellow.)
This lens produces sharp images with great colors and skin tones. It also has very good micro-contrast and is great for photographing people, art, food and all the things one encounters in street photography. In fact I feel it has the edge the Panasonic 14mm F2.5 in this regard. The bokeh is smooth and excellent. This lens excels in indoor photography where lighting is adequate but not too direct. I have got some excellent portraits using this lens in combination with my Olympus FL-300R flash in bounce mode.
From my brief experience thus far, I noticed that brightly lit scenes (especially with direct or indirect sunlight) to be slightly hazy, so a lens hood is recommended in these situations. Underexposing slightly, by setting my default exposure compensation to -0.3EV to -0.7EV, does seem to help with the bright scenes. I use a Tiffen 37mm UV haze filter and a collapsible rubber lens hood. Thankfully, the filter and hood on this lens, with hood extended, do not cause vignetting.
This lens seems to be slightly less "contrasty" than the Panasonic 14mm lens and is very sensitive to dust and even minor smudges, so a filter is definitely recommended to protect the lens. But remember to keep the filter absolutely crystal clear to prevent images from looking soft and veiled. (Good to keep a lens cleaning cloth handy).
Having understood both its strengths and quirks I now exclusively shoot in RAW + JPeg and develop the RAW images in Apple's Aperture software, mainly correcting for exposure, CA, highlights and contrast - and have obtained stunning results this way! (I typically need to do much less post-processing when shooting with my PL 25mm F1.4).
On a recent vacation in Portland, OR, I only had two lenses in my bag, the M.Zuiko 17mm F2.8 and M.Zuiko 40-150mm F4-5.6 R zoom lens. This combination gave me both the flexibility and speed in capturing the moments while on vacation.
In summary, this is an excellent lens, with caveats. I can easily recommend this lens to photographers who would take the time to understand how to use it.
Update: Oct 29, 2013:
Please see the comments for a link to some of my recent pictures with this lens.
Update: Oct 31, 2013:
If you intend to use a UV protective filter on this lens, definitely go with a quality, multi-coated UV filter. I used a cheap Tiffen UV Haze 1 filter and found it to be the cause of noticeable flare, especially against florescent lamps and neon lights at night. It is now going to be replaced with a multi-coated filter. Please see the comment for a link to my pictures showing this effect.
(I increased my rating of this lens from 4 to 5 stars, after removing the cheap UV filter and noticing a considerable improvement in night shots).
Update: Feb 3, 2014:
I managed to get hold of a 17mm F1.8 lens to compare this lens with. At F2.8 and F4.0, both lenses seem about equal in sharpness, micro-contrast and color. In fact you will need to pixel peep in order to find the differences.
Please see the links in my latest comment to this review, for the straight out of camera ("sooc") jpegs from both lenses and you be the judge.
I will go on to say that the unfavorable press reviews of this lens were probably because testing was conducted on a 12MB system, the standard when this lens was first released. On a 16MB system (like the OM-D EM5) this lens shines, especially with the weak anti-aliasing filter on the EM5.
Granted both Sigma 19mm and Panasonic 20mm are sharper than this lens. But the colors and skin tones that this lens is able to produce are quite amazing.
The 17mm lens format (34mm in full-frame equivalent) is one of the reasons I am sticking to the micro-four thirds format, even though I have now put together a basic Fuji X system.
For what this lens can deliver on my OM-D EM5, my rating remains at 5 stars.