So I bought one of these a little while back and have been using it for a few weeks, so here’s my thoughts for what they are worth...
It’s a solidly made product, finish is good and it fits on the Dremel smoothly. Alignment of the disc relative to the guide, whilst looking a bit cumbersome isn’t. I had mine sorted in under two minutes and I imagine most of you looking at one have sufficient aptitude to do likewise. The guides are pretty simply made and thread easily into the plastic housing once you get them started. I say that because twice now I have attempted to cross thread mine because I’ve not been paying attention to angles (best you don’t use power tools whilst drinking anyway

). My only real complaint, and again this is my doing, is that I didn’t swap out the 1/8” guide for the .040” guide when I ordered it.
I decided to put it on a new 2 speed Dremel so I had a dedicated grinder, my advice here is put it on a variable speed Dremel because the slowest speed on the two speed unit is a tad too slow and the fastest is too high by an order of magnitude. I’m guessing the sweet spot is somewhere in between and requires the purchase of the more expensive variable speed unit to find.
Putting it to use the grinds are consistent regardless of size guide and in this case the speed of rotation selected (although in high speed you need to keep it moving or you will flat spot it quite easily).
If you ball a tungsten beyond the tolerance of the guide you will either need to break it off or grind it on something else to knock the ball off first. I generally just break the contamination off but if you are just starting out that could get expensive.
I’ve not had any of the heat related issues noted above, and didn’t have any real hassle setting the cutting disc relative to the guide entry.
An unexpected benefit seems to be the 20degree taper I decided on balls off quite minimally and uniform on AC (I have an inverter) and is useful for thin material.
Pretty solid tool for the money in my opinion, and certainly quite a bit cheaper than any of the other similar styles of dedicated grinder I’ve looked at. Having said that I have no affiliation in any way with the manufacturer, my choice to purchase one was based on nothing more than seeing this thread (yet another tool I didn’t know I needed until GJ).