I went SGPro, originally cos I was here in the UK, but after looking into it I found it to be the best solution for me.
It has one of the lowest light losses of any adaptor, well built, rugged and has really nice Bokeh. There is a thread around here where someone did a shoot and compared different 35mm adaptors.
I was really pleased with my SGPro. There are other great adaptors out there including the Letus, the Redrockmicro and the brevis. it all depends on your needs.
For me I needed an adaptor on rails that was fast [little light loss as possible].
It does produce a flipped image so you'll need to compensate for that when shooting either by using a seperate monitor on your camera which has a flip image function both ways or that you can rotate 180 degrees to mount.