I think the d20 CoC is a good thing, for a fairly simple reason: WotC has (or at least had) a lot of money, and so they could afford to put out a gorgeous, full color book with creepy layout and a nice feel to it. Having borrowed my roommate's old CoC rulebooks, I must say I love the new layout.
As for other things. . . . Well, I'd never considered playing the game until, in the same 6-month period, I enrolled in a Sword & Sorcery Literature class, and CoC d20 came out. My lit teacher had us read Conan pulp stories and Lovecraftian horror, because Robert Howard was Lovecraft's friends and used some of his ideas in various Conan stories. And so I see d20 Cthulhu, all pretty and d20, and I decide to give the game a try.
If not for the WotC version, I might've read my roommate's copy, but I probably wouldn't have bought the book for myself. And if I didn't own my own copy, I wouldn't have wanted to use it nearly as much. So the D20 version is responsible for me getting into Cthulhu. That can't be a bad thing, can it?
Wait . . . this is the Mythos we're talking about.
Of course it can be a bad thing.