It sounds too good to be true, basically a $429 adapter to make an APS-C camera perform like a full frame camera. On the NEX-6 that's like a full frame camera that can shoot 10fps. It's designed by relatively famous (to photo geeks) optical designer Brian Caldwell, designer of the most lusted after but hardly ever used by real people Coastal Optics 60mm  macro. It's very well made, light years ahead of the cheap Nikon G to NEX adapters.

Metabones marketing:

1. Industry's best aperture ring covers a 8-stop range with half-stop markings, clearly indicating actual number of f-stops. No more guesswork! (Patent pending).
2. Compatible with both Nikkor G lens &  F lens (include non-AI & AI lens mounts).
3. Increase maximum aperture by 1 stop.
4. Increase MTF.
5. Makes lens 0.71x wider.
6. Optics designed by Caldwell Photographic in the USA (patent pending).
7. The tripod foot is detachable and compatible with Arca Swiss, Markins, Photo cam ball heads.

I ordered the Speedbooster to use with a set of Nikon primes, all old manual focus AI-S era lenses. I'd heard it didn't work perfectly with wide angle lenses, notably causing soft corners. So I wasn't too surprised when the Samyang 14mm f/2.8 and it didn't get along. Neither did it get on with the 24mm f/2.8. Well, ok 28mm is on the edge of wide and normal by modern standards, so I gave the respected 28mm f/2 a try on the adapter. Sorry, no corner resolution even at f/11. The Nikkor-0 35mm f/2 was just as bad, if not worse. To make sure it wasn't just the old optics, I tried the Nikkor AF-S 24-70mm f/2.8G with similar results. Above 50mm things were just fine, but 35mm and below, terrible outside of the central region.

To keep it short, if you're looking for that FX look above 50mm this adapter works like a charm. It really shines with the Nikkor 105mm f/2.5 AIS. On the other hand, if you want to use wider lenses and have them still be somewhat close to their FX focal length, well, this isn't a magic bullet. I'd hardly call it useful wider than 35mm, by the time you stop down enough to get a sharp image frame to frame, diffraction is robbing sharpness.