Not the one people were actually talking about, but Rosebud (in Davis proper, where Summer and Elm split, also a diner car) has a reasonably good breakfast as well. It's a small place so there's a wait, but I've never felt particularly rushed there. The one time I was at Sound Bites, I did feel very rushed, and didn't feel like the food was particularly spectacular.

The other canonical localish breakfast place is S&S in Inman Square. There's a Bickford's on the far side of Winter Hill from Magoun, which is just enh.