I like him. I feel like he does a really good job describing the action. My tv is still in the shop so I've listened to nearly every game on the radio this year. I feel like I can follow the game fairly well listening to him. I don't think he's quite as good as Pete overall, but maybe a touch better for radio. Seems a bit quicker describing the play and throws in more details about what set things up while Pete waits for Crisp to fill in those setup details.
One thing Pete does when the other team scores is tend to finish describing the play and not telling me they scored for a few seconds. Callahan says "and they score..." right away and I prefer that.
I preferred Pete and Crispy, by a fair margin, over Eli for radio, but am happy with Callahan.