I'm waiting for the May update to see what happens from there before buying another flashcart that works on the 3DS, but I just have my R4 Ultra with AKAIO on it, which works great, but my old DS died (I was replacing the shell - one of the cables to the top screen or the screen itself needs replacing. Dunno which), and it won't work on the 3DS. I tried it, and it just crashes the 3DS. Well, it gives me an error screen. It comes up as R4 Ultra though, when I put it in.
I used it before I heard what Nintendo had to say about flashcarts and the 3DS so.... I'm hoping that annoying little record of the R4 won't cause my 3DS to get owned by Nintendo. Short of resetting the entire console (dunno how much data it'd wipe, and I don't really WANT to know), I don't see how I can get rid of any traces of the R4 (even deleting it from the Games Library doesn't completely get rid of it). Nintendo, please have mercy on me.
But yeah, my advice is to WAIT. It's just over one more month until we get the update. You can survive in the mean time (I HAVE to. I don't even have the money to buy any new games, 3DS ones when they come out or otherwise, so I'm just enduring).