The creatures are stronger, faster, and tougher than their gene donors, and are capable of interfacing with machinery and digesting living creatures. Their biosnythetic composition is extremely light, hard, and durable, so their claws can penetrate steel. Unlike most nanotechnology, they have a distributed cooling system that protects them from overheating; you'd need to throw them into the sun or keep a sustained plasma beam on them before they'd start to lose mass.
They do have weaknesses, though. Cutting them into small pieces will render that mass inert, and low temperatures can freeze them solid. A cryonic weapon, followed by a concussive attack, can freeze and shatter them into harmless shards. Some forms of technopathy can also theoretically effect them, though their firewalls are godly. Their greatest weakness is their lack of true intelligence; they can be outwitted, either tactically, or in conversation.