I benchmarked AIR against Tcl/Tk on my desktop by implementing the same app in both - it used something like 80x the memory and 20x the CPU IIRC. It's not even a good GUI toolkit, let alone a good cross-platform one, compared to tech from the 90s.
That's a ridiculously biased comparison - of course tech from the 90s will use less memory and CPU, that was a higher priority in those days. A more relevant question is whether AIR was easier to develop in, or resulted in something that looked better.
