So I gave the Witcher a try, and it has been a pretty mixed experience. Construction is ok, I guess, albeit on the heavy side clearly (must be some cast metal alloy inside)
Comes with two size rings to protect your attachment, as it is a side-by-side design (SBS) It fits the iHeat as well as all three versions of the Project (OG, Eraser and Pure SF) but I don't think it would fit the Splinter.
It is thumb operated as the trigger is on the top. Feels strange at first but once you hold the whole thing in your hand it makes sense and it's fun to use. The way you grasp it, it feels compact and small. Definitely feels better in the hand that what it looks like (looks are not very convincing at first glance)
But it's not overly small either. Here you can see it next to the SmoAnt Knight V2 (my current favorite) and the Joyetech evic Primo Mini (upside down on the picture because I was too medicated apparently):
I'm not a fan of the screwed battery cap, takes a lot of turns to open/close and prone to threads stripping over time. I much prefer magnetic covers. Not a fan of the big name on the sides either...
But the number one show stopper that prevents me from recommending this device is that, at least on my particular exemplar (but it appears I'm not alone) TC mode is simply not working, or I must be doing something terribly wrong. Whatever I try it reverts back to Power mode. This is so annoying.
I contacted fasttech and they told me I could RMA the damn thing but it's too much hassle for me. Alternatively they offered to refund me $10 and I keep the device. So for those interested, you could buy the Witcher on their site and get a $10 rebate just by sending them a video of how it fails to operate in TC mode... or if you are lucky, who knows, you might get one with working TC, in both cases you win heh!