3 things that don't work
As a spectator I can:
-see both teams failed surrender votes and tell my friends in the game, even if it's 3 minutes late it's still relevant information.
-call out every shrooms that Teemo puts down, even if it's 3 minutes late, it might prevent someone from dying on a shrooms after fleeing from a close fight.
-give my friends in game the timer on a creep like Baron or Dragon if the enemy team got it.
I suppose making the delay 5 minutes would work to counter those flaws but I have a feeling there is a reason why you guys at Riot decided to stick with the 3 minutes mark. Is there? Could you reply to this thread/question please?
Other than that, spectator mode is AWESOME!!!