While I agree that the slowdown is very noticeable once the MBA gets hot to the touch, I joke that it's a feature, encouraging you to take a cooldown break every once in a while :-)

More seriously though I agree it depends on workload. If you've got a dev flow that hits the resources in spikes (like initial builds that then flatten off to incremental) it works pretty well with said occasional breaks but if your setup is just continuously hammering resources it would be less than ideal.