Excellent Episode
Even though it has been 16 months, this episode showed that you've grow in skill since the last one. The increased use of 3D effects showed it.
For the most "I want it ASAP" crowd (Which I am not, but I do know some that are), the length of this well made up for it (which is maybe two or three episodes worth crammed into one?). It was to the point where I though, "Is it going to end? Please don't let it yet." In the end, I'm glad that this "Minus World" story arc is contained into one episode, because helped set up the next one.
For the old school flavor, the switch to 8-bit is great, the redesigned sprites as well...and the sound effects of that world too. I especially like the backstory of the Minus World.
If I have to give out one negative comment, it is that seeing a smooth vectorized arm cannon with Mecha Sonic's pixelated sprite strikes me as very odd, especially since we see it as a pixelated sprite on the side view.
Overall, I like it, and I will be looking forward to the next episode. And release the next one soon (as in not another 16+ months. Wanna know what's evil? Releasing the next one in 15.9 months, because it is technically released in less than 16 months). If not, C'est la vi.