I would say the appeal of Ace Attorney is the goofy characters that give the series lots of character, yet it isn't condescending and isn't afraid to have serious moments now and again. For murder mystery type stuff I find that the solution is usually exactly what you think or the opposite of that, but with Phoenix Wright the truth is always so complex and deeper than it initially seems. There are many times on a case near the end where I feel that they could have called it a day and left it as is, but they always introduce more layers of crazyness, more twists, more bait 'n' switches.
I agree with the fail state being bad though. It either forces you to sit through speed up dialogue wasting your time, or to constantly save also wasting your time. I'd like to see something like what they had for Layton Vs Phoenix Wright where answering correctly gives you additional picrats so you can unlock extra features like the music, character models and cutscenes faster. But if you get the minimum amount of points possible you still have enough points to unlock everything by the end of the game.