I think it's great if you are good at building your own, but they are only good if you know what you're doing and have even a fraction of the experience that some of the well known custom wheel builders have.
I've done it, the wheels were ok for the time i had them, but it's a pita and I probably wouldn't do it again if I didn't have to.

But that's kinda the point. A good custom built wheel won't need tweaking, and even if it does years later you can still tweak it just as easily as if you had built them yourself. This isn't really a selling point to building your own.

Just sayin, I know just because it's a "custom built" wheel, that doesn't guarantee you squat... but building it yourself isn't necessarily any better.