I have both the II and III.
The III is slight improvement over the II at this time. The amount of improvement, combined with the lack of an available foot controller, does not justify an upgrade at this time.
What you gain in ease of use editing, you lose in live performance. Is that trade off worth $2500? Of course not, buying the III TODAY is about the future and the potential of the unit.
One thing I will say is have not been able to get the tight rock distortion sound on any FW after 18.09. Quantum was great for medium grit, but III too lacks the tightness I get from preQuantum firmwares.