I've had the v2.5 donut for about a week now and wanted to share my findings so far.
Battery:
I reached out by email and Matt recommended I pair the donut with a Joyetech eVic-VT which I was able to find on ebay easily enough.
The temperature mod technology is an amazing step up from pulsing a fixed voltage or wattage, and I love how it backs off automatically before getting a burnt taste.
As some have mentioned above, the temperature is determined by the drop in the resistance of the atomizer as the ceramic heats up.
This does indeed work well but I highly suspect that the temperature displayed is not the true temperature as the readout is calibrated for nickel wire.
It would be a very interesting project to characterize the temperature vs resistance change of the ceramic itself, theoretically VT batteries whose software can be updated could add ceramics as a separate mode.
The battery itself is a solid performer but I'm still looking for a temperature mod in a cylinder style which would be flush with the ceramic head.
It also makes a faint humming sound while not in use and is a bit bulky (I don't need weeks of battery life).
I will be trying my 510 threaded ThermoVape Evolution battery soon (they look very sharp together) but have held off because I'm worried about cracking the donut from over-voltage as it's purely mechanical.
Atomizer:
I'm pretty picky about my vapes, preferring all stainless steel and glass for juices but this ceramic's fantastic handling of solid concentrates won me over immediately.
I love the cleanliness, solid feel and size of the ceramic head.
The airflow and clarity of flavor are by far the best I've ever seen in a portable oil vape.
The natural flavors of high quality concentrates come through bright and clear with no added tastes, possibly even better than a traditional nail due to the super low temps.
Waxes/shatters are easy to drop in but the deep bowl has made loading stickier oils much more difficult.
The oil gets stuck to the upper walls and isn't close enough to the element to melt and slide down, eventually resulting in
a situation similar to GoGlass's.
I will be getting the short wall version that Matt mentioned in his video as soon as he will agree to send me one, and I will be purchasing the v3 (and inevitably the v4 and v5) when they become available too.
Although it's near perfect as it is, there is a lot of room for creativity in future version of the crucible.
Possible ideas could include placing the element underneath the crucible for indirect heating or a ceramic knob in the bowl (or wall or cap) that can be used to scrape the oil off a dabber.
Divinetribe has completely surpassed my expectations on the quality of these atomizers, if you are on the fence jump in and grab one immediately.
I think both portable and wired e-nails will need their own forum sections soon as they are clearly the future.
Best of luck Matt, you're doing a great job!
ps. The 5/16" ID tubing for my Arizer ExtremeQ's whip fits snugly over the mouthpiece which can be fun when lifting the battery becomes more arduous near the end of a session.