I tried the kobe beef burger at Ruby's (Fullerton location). I'm not sure if it's a limited time special. It costs around $10, IIRC ... my dad paid the bill.
I ordered it modified, with sauteed mushrooms and no lettuce, tomato, or mayo. It comes on a special bun, with your choice of cheese. It was a superior burger, but my assessment should be discounted because I rarely eat hamburgers. It was very juicy and slightly crumbly. On the negative side, it was a little too salty ... and my salt tolerance is pretty normal.
Since there are many good reasons to visit a Ruby's, IMO, I recommend dropping in and giving it a try.