Concerning the MD 1kg rule plates, they are pretty good quality. IMO, they are better as far as fit and finish, and weight accuracy, than at least one IWF certified brand. We sold a lot of sets of the WFW 1kg rule plates for around $159 a set, and the MD plates are definately better looking and closer in weight than those were, and quite a bit cheaper to boot.
If you are still looking to file down pound plates, I have tried it. Its hard. If your dead set on it, using a drill press to drill holes in the plate till it weighed right was easier for me than grinding. Looks pretty bad when your done, but most of the time that doesnt matter, and it doesnt take all that long if you have a decent drill press. Would probably be a real pain with a hand drill, though.