Actually, I'm quite happy with my MicroMark punch set.  Not only is it useful for the disc punching out of plastic, I used it to punch tying holes into my Lee Valley wood veneer custom Christmas gift tags too!

I've found that it punches a pretty good disc.  My punches don't seem to have any glaring irregularities.  9 sizes for 30 bucks is a pretty good deal, IMHO.  Anything smaller and I would just be using sliced styrene rod anyways.