Easy there 777236ER ... its a discussion, not an argument.
I'm certainly not an expert in nozzle design, but I just seemed to remember a picture from one of my old propulsion books that showed an RB211 with this kind of mixer and it struck me as odd that they're still using something like this.
Apparently a variant of the blowtorch is still in use, or at least the picture on Rolls-Royce's website is outdated.
411A, I'm confused as to making an exception for the mixer being used for the hot stream. I was of the impression that the purpose of the mixer was to mix the turbine exhaust flow with the cooler free-stream or bypass air for two main reasons.
First, to mix the cooler, denser bypass air with the core flow to quiet noise from the combustor. Also, to energize the column of air surrounding the core exhaust. There is a significant difference in the gas temperatures and velocities and a lot of shearing going on. It seemes like you don't want to do this (wanting high exhaust velocity in high-speed cruise) and would be good for only low speed, quieter flight.
Another point in the case against 'em; these mixers live in a very high-energy part of an aircraft and, I believe, have been known to crack and deform.