Summary: I boutght it because I know it is a good one. But when I opened it, a part in the rear cap to hold tightly the aperture(?) in the lens was broken. I tried to contact customer service but they never relied. Anyway, good product and excellent picture.
Summary: I bought this lens after looking at the Nikon 35mm 1.8 & the Sigma 30mm 1.4. I went with the Sigma due to being able to shoot at the wider aperture. I heard a lot about sigmas QC issues and this lens was one of those. It wasn't sharp at all at 1.4 until it was acceptable at 2.8 or so. It also had back focus issues, especially in backlit/low light situations. I sent the lens off for a warranty repair, and its better now.
Pros: 1.4 aperture is handy in low light situations, Feels pretty solid
Cons: Lens hunts for focus in low light/backlit situations, Not as sharp at 1.8/1.4 as I'd wish.
Summary: I purchased this lens 3 weeks ago from B&H and was excited to use it. The lens had two issues. First. focus was close but a bit off front to back (focus on eyes and nose is tack sharp & eyes were a bit soft...) and the exposure was consistently 0.7 stop over. The exposure issue was easy to solve with EV -0.7 on the D300 but the focus in manual and auto drove me nuts.
Summary: Reading the specs on this lens it promises to be a great lens. For me I love the 60mm FOV on my E3 and the 1.4 aperture is perfect for the portraiture I specialize in. I was hoping this lens would make up for the obvious gap Olympus has in the fast prime area but it just did not cut it for me. I went through two different lenses and they both suffered from the same issue, off mark focusing.
Summary: I am a professional photographer and use my equipment primarily for portrait (environmental) photography. I was hoping this lens would be able to compete with my Olympus 50mm f2.0 and provide faster AF. It definitely focuses faster but it is very soft in comparison. This lens is very well built and has a very tactile feel to it, too bad the glass is not as good as the metal. Would have loved to have that 1.4 aperture.