Pyro negatives, especially PMK negatives, are GREAT for scanning. The stain makes the contrast appear lower to the scanner, and as long as they're not too dense they actually seem to scan easier and with less worry about losing highlights or shadows in the process. To be honest, I often wish they printed as easily as they scanned.
One thing...DO scan them as RGB files, then convert them to gray as soon as they're scanned. I tested this once not long ago and found that there is pretty considerable difference between the tonality of pyro negs scanned RGB and grayscale.