I got my Thumbs Up Model 1 [the shorter one] two days ago, and had a chance to shoot in low light with it attached to the M8 last evening. Tim Isaac has done a wonderful job in executing a terrific idea.
The finish is great [I don't mind the logo], fit is exceptional [no slop] and it falls exactly where the film advance lever on my m4/m6 does when it's in its ready positon away from the body. It doesn't so much provide a hold that carries the weight of the camera [which others have expressed concerns about, as they fear it would loosen the accessory shoe], as it does provide a balancing point, securing the grip of the whole hand. This is what the film advance lever manages to do on other M's--you don't hold the camera by it, it helps support the whole grip. Really a plus with my 75 Lux and 35mm C-V Nokton. By the way, I'm left eyed and wear glasses, and there is no interference from the Thumbs Up.
Packaging's neat too, and delivery was swift to the US from China.
Highly recommended. Great job Tim!