Haha, I like how the two people that posted about K-Akuma are from the place where I tried to perfect him (CSULB). But alas, I traded in K-Akuma for a more superior K-Morrigan (IMO).
But check out the Wiki, I put some K-Akuma info into it.
The benifit K has is that the defense boost really helps akuma because of his low life. As well, you can’t really waste meter on a Raging Demon like you would in N/C/etc, because it’s going away anyway. The downfall is once people know its coming… you’re hard pressed to land it. The benifit is when they think you’re going to do it all the time, you get free bnb combos when they wake up-> jump to avoid the demon.
JD doesn’t hurt rushdown, in fact it can cover you in some places since you can JD one frame earlier than you can block. Plus, you can rush in and Jd some laggy attack that would normally push you out, and instead punish them. It also gives you a bit of a fallback plan in jump->JD as long as its not abused.