My limited understanding is that metal parts made by additive processes can end up with poorer lifespans than forged or machined parts. You get different layers which melted and cooled at different times, with weird residual stresses. Parts can fail sooner and just be weaker.

If your prototype only needs to live long enough for you to iterate on it, that might be great. But it might not be suitable for real world use for an extended period?

I’ve read that Rolls Royce is going to be using 3D metal printing on their upcoming Advance3 engine. If it’s good enough for those operating conditions then it should be good enough for anything.

Supercars aren’t exactly known for their reliability. I imagine Porsche would use this on their super and hyper cars first.

Powdered metal camshaft lobes have been in wide use in production vehicles for several decades.

Powdered metal parts are everywhere today, but it's not really an additive process - you pour a bunch of powder into a mold, compact it, and then bake it.

PM parts are also porous and fairly weak (in some dimensions) relative to machined counterparts, so you don't typically see them in critical applications.

Yeah, now that you mention it, camshafts have quite a reputation for fragility. I always wondered how a rod of solid steel could fracture like that.