Letus is nice but be aware that with Extreme version you won't be able to stop your 35 lens down past f4.0 (ground glass pattern becomes visible). Shutter speed faster than 1/100 and you got the same problem. This is true for all vibrating adapters. Ultimate version is rotating one, free of this issue, still loosing only half stop of light but its $$$.
You might have a look at the SGBlade adapter once it's released (which should happen soon). Their older product, SGPro, was famous for its beautiful bokeh. Blade's gonna be even better - it's rotating (no groundglass pattern problems), little light loss (although slightly more than Letus), two grades of groundglass to choose from, very well built and should be way cheaper than Letus Ultimate.
Redrock M2 looses too much light and many people have problems with edge-to-edge sharpness, too.
