Audio Nodes are subject to garbage collection delays. This effectively makes the API no-go for live performance situations. (I know you can't fix it either.)
Parameter change specifications contain either an analytic or a mutable form, but in practical implementations, both forms become desirable to implement efficient processing that can also begin at arbitrary times within the envelope. I cancelled my implementation of the API after discovering that the lack of detail in this section made for a fragile, confusing, trial-and-error situation to prevent discrepancies when comparing the results of the analytic form against the mutable one.
Rendering does not appear to have any automatic regression test available. Web Audio needs an Acid3-style test.