I agree that the Ki-84 is faster than most think it is. It has one major drawback to me though. It likes to jettison its wings at speeds of about 425 and above. So I can only manage maybe a 2k dive before I'm reaching critical speed for the wings. And yes, I know I'm flying a paper airplane. I do love it's cannons though. They have an extremely high ROF. I burn through 300 rounds really fast if I'm not careful.
You can safely dive it at about 450 mph. Above, you risk tearing something off, mostly both elevators: honestly I never shed wings. Compared to other jap planes, yep, it's harder for it to take fire, but not THAT hard, after all. The one thing I really hate, damage-wise, it's pilot wounded... 8 out of 10 times, it's the first thing I lose.

The gun package is really good.