[anonmeow]

The ribosome, DNA replication complex and ATP-synthase (and other complex enzymes) qualify as precise molecular manufacturing, if you relax the definition a little. Ribosomes are already being engineered, see expanded genetic code.

How far could we go by modifying existing biological molecular machines? Probably quite far.

[eli_gottlieb]

That's true, but those all work precisely by taking advantage of thermodynamic jitter to get things done.