Well, like I said, they're only bad in the sense that they're not *absolutely* awesome
. They're still good for their price.
They're also unexceptional MR, mindless, low move prot 0 size 3 undead. Which means they have quite a few weaknesses that are readily exploitable even with minimal research. At the same research level Spine Devils might be magnitudes more expensive, but I feel they also give you more bang for your buck in most situations.