It is worth getting the right thing for tonal transparency. All pickup covers affect the tone somewhat thanks to eddy current losses. Plated brass is the worst and pure nickel silver (A.K.A. "German" silver) is the best. There is also a bit of a microphonic effect, but that can be minimised with proper potting.
Just beware - there are at least four different polepiece spacings: vintage Gibson - 49.2mm; Modern Gibson - 50mm; DiMarzio F-spaced - 51mm; Other F-spaced - 53mm. I say "at least" because I've run across everything from 48mm to 54mm.
I do need a pair of covers, but would prefer chromed nickel silver and need a DiMarzio F-spaced for the bridge (51mm). I'm probably just going to get a pair of Schaller open covers from Guitar Jones:
They work on any spacing, protect the coils and provide a good fit for humbucker mounting rings and the design helps make them pretty transparent.