Difference-maker, no.
Probably the closest to a "real" point guard as there is on the roster.
Still their third or fourth best player? Yes.
The Cavs losing Delonte is, I think, analogous to our losing James Posey last season. We subbed in players like TA that were no where near good enough to replace him, just like they may be forced to give too many minutes to Boobie Gibson.
I think they lose a little of their intensity, which is going to flow through to how well they play defense. Their backcourt rotation is now going to be Mo Williams, Boobie, Anthony Parker, and Jamario Moon. Does that really look like backcourt that's going to be able to slow down Rondo? They going to be able to keep Ray Allen and Eddie House from getting open looks?
Wonder if they would have tried bringing Wally back, if he wasn't going in for surgury?
If they can pull off a trade for S-Jax, I'd be worried, but the question is whether they have the pieces Golden State would want to get a deal done. S-Jax would help them out tremendously on all fronts; size in the backcourt, defense, intensity.