As long as there isn't anything that can come out of the pits, its good to use. It isn't as efficient as it could be, but you won't be able to measure that difference.
Sorry smukc, but I wouldn't put that oil pump in my engine, and I sure as hell wouldn't put it in your engine. I have built quite a few alfa engines, and this pump simply isn't up to factory specs. If you can't return it, you might be able to get a coating company to coat the pump and internals with an anti-friction coating. This is assuming that all the other clearances in the pump are o.k. As has been mentioned, the actual effect on measured oil pressure will not be noticeable, but you don't know what other unseen flaws the pump has.