I Am Bread is for a very special kind of gamer. It's for a patient soul, someone who appreciates the absurd, and someone who wants a break from the norm. I appreciate I Am Bread for what it is and the hilarity that comes along with physics based games. But it's a take it or leaven it deal in this case. Either you'll love I Am Bread for its quirky charm, or you'll hate it for it's challenging and thin gameplay.
I'm of two minds when it comes to Xeodrifter. It's an homage to a game that I absolutely love, and Renegade Kid did some truly commendable things here. On the other hand, I didn't get much excitement from exploring its worlds. It's a game that will only appeal to the gamers that grew up with the games that inspired it, and even then, it might leave you wanting more.
As for whether the DLC is worth the price of admission that will totally depend on the individual buying it.