If TARDIS's were real, who wouldn't want to go back and see what things were like? But to observe it would be as far as it goes for me - I don't think I'd want to stay anywhere but now. So much we take for granted would be missing. Despite the arguable bonuses of social cohesion and no pervasive ring tones, there was lack of healthcare, high infant mortality, diseases, lack of food, no central heating (yes, I know, aside from the Romans), working until you drop, wars, religious fanaticism...
Come to think of it, maybe things haven't changed that much?
