Concerning the use of other adapters on top of the EOS SB for NEX, if you go to the metabones site for the EOS SB they have the following showing as "NOT SUPPORTED"
EF-S lenses
NEX-VG900 (see note 4)
Lens correction such as peripheral shading, CA and distortion
Focus confirmation "chip" (e.g. Dandelion)
M42 screw mount adapters (see note 6)
Stacking non-Metabones/non-Conurus mount adapters on top (see note 7)
And here are the included notes...
Note:
1.Requires lenses supporting distance information.
2.Autofocus disabled for Contax N and Contax 645 lenses.
3.A third party zoom lens may need to be registered with the Smart Adapter first in order to detect its maximum aperture. Autofocus is disabled for most third-party lenses.
4.This Speed Booster™ is designed to cover an APS-C image circle which is not big enough to cover a full-size 36mm x 24mm sensor.
5.Sony NEX cameras cannot display aperture values beyond f/1.0. If a f/1.2 Canon EF lens is used with the Speed Booster™, the resulting aperture is f/0.9 but the camera body displays f/1.0.
6.Some improperly-made M42 screw mount adapters may short the electronic contacts of the Speed Booster™ and cause damage to the Speed Booster™ and/or camera body.
7.Some manual focus lenses (e.g. OM 28/2.8, OM 50/1.8, Leica R 15/3.5) have rear protrusions which would damage the optics and/or housing of Speed Booster™. They need to be modified before they can be safely used on Speed Booster™.
Here is the direct link to the page.
Sony NEX System : Canon EF lens to Sony NEX Speed Booster
This is a little disappointing as I was hoping to buy the EOS SB and stock up on EOS adapters. Oh well. We will just have to try them out and see which ones work correctly. I am really waiting for the Minolta SR to NEX SB anyway. Or possibly the Sony Alpha SB. I really want to use one of these with my old Minolta glass, both MF and AF.