It's interesting too... I think I am against it... they should just have strong protocols and prevent anyone concussed playing a further role in the game...
Unclear why someone who is hurt in that way can be replaced, but for example the Simon Jones knee, or the horrible Gillespie/Waugh situation can't (although I guess under this rule Waugh might have)...
Should be for all injuries or none - Smith gets his arm broken, can't be replaced - gets concussed can... bit weird imo... and not like concussions are that common... at the end of the day, both hits were similar - quality quick bowling and Smith getting himself in the wrong position