Viltrox EF-M2 Speed Booster 0.71x Focal Adapter - anyone using one, or similar?

Just bought a Viltrox EF-M2 speedbooster for my Canon M5. It should arrive Wed., Dec. 19th. Do any of you have this adapter or similar, and have you seen any variation above or below your expectations? Several reviews stated image quality is not compromised a lot. The two lenses I was most interested to use with it on the M5 the 85mm 1.2 ii and 16-35mm f/4 IS. I also considered the Rokinon 12mm f/2 but apparently it's more like an 18mm on the M5, and unless I misunderstood, 16-35mm with the Viltrox adapter should remain closer to 16-35mm. So I opted for the adapter rather than an extra (manual) lens.

The image quality is decent. A question mark lurked from the M5 screen, but once in Lightroom, the photos were as good as hoped for. I didn't buy this for top-notch images, but extra versatility when I want to use the M5 as an extra body to get a few more photos that could be printed 5 x 7 to 8 x 10

Here is the Canon M5 & Canon 85mm 1.2 ii shot at f/1.0

With the Canon 16-35mm f/4 ... it seems the Viltrox adapter makes this lens function like an EF 11-28mm f/2.8

I like the booster so far, have tried various lenses on it with my m50.

Here is a test shot from my 5D4 vs M50 just to see the 1.1 crop factor now on the APS-C. f2.8 on the FF, f2.0 on the crop...

The only thing I think I have seen that I don't like, but wasn't necessarily a surprise, was the impact on IQ on the edges. It is to be expected though, given what the booster is really doing. Also some lenses vignette pretty bad, and that is likely due to the lens just supplying enough of an image to cover a FF sensor and the booster is shrinking that image circle down too much.

TeamSpeed wrote in post #18774331
The only thing I think I have seen that I don't like, but wasn't necessarily a surprise, was the impact on IQ on the edges. It is to be expected though, given what the booster is really doing. Also some lenses vignette pretty bad, and that is likely due to the lens just supplying enough of an image to cover a FF sensor and the booster is shrinking that image circle down too much.

I didn't look for vignetting yet, but will watch that later. It seems that this Viltrox would be fun to try a wide prime like Sigma 14mm 1.8 ... or Irix 15mm 2.4 ... or Irix 11mm 4.0

An 11mm on the M50 or M5 would be fun. The Irix 11mm would go to f/2.8 ... I sort of like the "Blackstone" version.

The Sigma 50 1.4 (old version, still works and is pretty sharp wide open) works well with the booster.

Partial crop, followed by full crop of original image:

I own a Viltrox Nikon F to Micro Four Thirds and I'm really happy with it! It brings the 2x crop factor down to 1.42x so I'm actually getting wider than APS-c which is nice. I haven't used it as much as I should, but I loved the results I got from my Voigtlander 40mm f2.

IMAGE LINK: https://flic.kr/p/2av4​K2F