I have an EZ4 and yes, it's problematic. I found it was better (not great, but better) if you use Japanese audio. I think you hold L when you press start on the title screen. You should hear a Japanese voice say "showtime" if you did it right. Some glitches were better after I did this.
Still, save every opportunity you get. I was able to complete the game, and got just about everything unlocked, although it is annoying when you lose 15 minutes of play time due to a freeze every so often.
it works fine for me, its your micro sd card, get a fast one and its fine, its only crashed for me when i opened and closed the lid once too fast.
I have problem with both (J) and (U) versions of the game... random lockups... and no, there is no solution for the problem.
someone said to me that having only one game (Castlevania) and format it with 64K clusters would probably make it better... but none of those two solutions did anything. and defragging a formatted card doesn't give anything.
so, YOU and I will have to order the game whenever we can afford it. Or we could snag some other hardware such as the EZ5. But since I've heard it gets slowdowns and gfx glitches in some games, maybe going for a M3 would be smartest?