I imported the HRAP4 a few months ago and I've been playing Injustice on it since. I was already familiar with the hayabusa and kuro from the Fighting Edge (damn shame that stick is not compatible with the PS4...) and I have a modded HRAP with full Sanwa parts.
Like the poster above, I've never been a fan of the kuro buttons, they have a tendency to stick (rarely) and don't permit as light a touch as the Sanwa OBSF-30s. Let me tell you, when I put my Sanwa HRAP3 side by side with either the HRAP4 or the FE, the difference is clear as day and I will be swapping out the HRAP4 kuros soon (I'm leaving the FE stock for sentimental reasons).
I actually do prefer the Hayabusa stick to the Sanwa JLF, so that will be staying.
The HRAP4 casing and button placement is superior to the HRAP3, in my opinion. All in all, it's comfortable and sturdy. The body is narrower than a TE, which suits me fine.
Now all I need are more games to play on it!