The 75/1.8 m.Zuiko: (Tested on the E-M1 with firmware v 1.1.)
The m.Zuiko lenses, for Micro-Four-Thirds (mFT) cameras seem to be divided into two or three categories. Those in the basic consumer (standard) line are low-cost, mainly plastic-bodied lenses. They won't stand up to the rigors of professional use, but in the hands of the average user, they provide good optics and give excellent value for the money. One, the 12~50/3.5-6.3 EZ is weather-sealed.
Above the consumer lenses stand the Premium and Pro lines. The premium are prime lenses feature absolutely top-quality optics that will hold their own with any lenses, no matter where they are made, and a professional, all-metal build that will survive professional use. Again, so far, just one has been made with full weather sealing - the 60mm 2.8 Macro. Starting with the latest 12~40/2.8 zoom (classed as "splash proof"), the PRO designation has been applied. The PRO designation is to be used with the coming 40~150/2.8 zoom, which will also be weather-sealed.
The PRO designation seems, at this point, to be reserved for constant aperture zooms. However, the coming and the 300/f4 super-Tele prime lens (due out in early 2015) will gain the Pro designation, as well. if you want the absolute best lenses in the line-up, the Premium or PRO grade prime lenses are the way to go.
When I was young, lo those many years ago, I shot with a Nikon F, which was the professional's camera of the day. But, I could only afford two lenses. I had my wide angle lens (the 85mm f1.8 Nikkor-H short tele) and my normal lens (the 200mm f4, Nikkor-Q). Those three peices remained my "kit", for the next 18 years. And I loved them!
So, unlike many, I've always seen "long". Thus, the m.Zuiko 75/1.8 Premium lens (with its 150mm equivalent field of view) fit right into my photography like a hand in a glove.
What struck me first, was the fit and finish of this Japanese made lens. The all metal lens is finished as well as anything I've ever owned by Leica - who are generally accepted as the gold standard for photographic manufacturing quality.
The focusing ring is silky-smooth. Because it is a focus-by-wire system, it does not have the resistance of a real, manual helicoid focusing threads, but the system is very responsive, with no overshoot - a problem with some focus-by-wire systems.
Still, the manual-focus abilities are almost irrelevant, as the fast 1.8 aperture, combined with the lighting fast, and deadly accurate AF system in the E-M1 are so good, I doubt you'll ever need to use the manual focusing!
I was disappointed to find that the lens does not come with a matching lens hood, and that Olympus want $79.95 + tax + shipping for their LH-61F. So, being a thrifty soul, I purchased JJC's J61-F lens hood, on eBay, for $29.95 including shipping, and with no tax! It is beautifully made and while I cannot prove it, if I were a betting man, I'd bet that JJC (or whoever actually made the JJC) is the OEM who also makes the genuine Olympus hood. I can see no real difference, other than the label - and the price!
There is little to say, beyond this, except to say that the optical performance (that's why you buy a lens, isn't it?) is simply stellar! I've not been as happy with a lens, since I purchased my Leica 90/2 Summicron! In fact, though I've not done any scientific testing, I suspect the 75/1.8 Zuiko is sharper than my Leica Summicron!