I've taken only two Vivarin pills tonight (they keep you awake). I checked to see the effects of Speed, and I feel every single effect from just goddamn caffeine pills. Effects include:
feel alert and energetic
be excited or agitated
talk a lot
feel aggressive
feel anxious or panicky
your heart beats faster
you breathe faster
you feel less hungry
your blood pressure rises
the pupils in your eyes get bigger
you move more quickly
it is hard to sleep.
I'm not sure about the pupils thing though. The moral of the story is, I don't know