I like him -- more as a studio guy, but OK with him as a part-time color guy. Color guys often take a while to become seasoned. Max was awful early on, as was Jerry Remy. They were both criticized in a big way early in their work as color guys.
But my guess is that Donny will get a national gig in the near future. He's decent looking, reasonably articulate, a young guy who played with/against a lot a current players, and he comes across pretty affable as well. I see him as more of a studio guy, but I think he'll get increased national notice in the next few years. Someone else will be Tommy's replacement.