Updated final edit after owning and racing this thing for 6 months:
Don't buy this radio. It shipped with firmware that caused the car to randomly lose signal and stop on the track for like 5 or 10 seconds at a time. The first time it did this to me was near the end of a main, causing my only DNF of the season. Sometimes it lost signal while keeping the car at full throttle. Thank god I wasn't running my ebuggy when that happened. Even after multiple firmware updates that solved most of this issues, one of my cars still has occasional full throttle runaways that would last around 5 to 10 seconds. It is simply not a reliable radio and I a no longer trust it.
Aside from that, the UI truly is unintuitive and needlessly complicated for surface use. Despite this needlessly complicated UI that advocates will tout as being capable of advanced functionality beyond anything else in the surface market, there is nothing you can do with that functionality that justifies this radio over a simpler to use option.
After racing with this radio for 6 months, I finally went back to a Noble NB4+ and instantly went faster - I feel I have a much more direct connection to my car. I can make it do what I want with significantly less effort than it took with the MT12. It just feels more precise. It does this while being able to drive the steering servo in my 2wd to its full extents whereas the MT12 in it's lowest latency mode could not. The only way to get the same endpoints out of the MT12 that I get with the NB4+ is to switch the MT12 to a higher latency operating mode.
The reality is this is a product being marketed as "top of the line," but completely falls flat at the most basic functionality required for a radio, but even when it does work, it still comes up short compared to other actual top of the line products in the market. The reason why this is the case is simple - RadioMaster is a company that took open source projects for flight applications developed by amateurs and crammed it into a surface radio without even bothering to make sure it worked right before charging you $130 for it. You get what you pay for, and in this case $130 doesn't get you a product made by a company that actually puts effort into developing and testing what they sell.
Another update: here's a video I made showing I'm using firmwares with the signal dropout fix, the fw's match on both the TX and RX, and that I've got my failsafes set correctly. Despite all this, my car has a full throttle runaway.