honestly ive done the ghetto Sugar yeast bucket and ill tell you IT HELPS but only as an additive (also allows for hotter rooms)
you will always notice a little boom in your plants when you have a high ppm level
if you want to see what co2 can do get a brick of dry ice your local grocery store will have it (not usually Wal-mart) and put it on top of your lights (or above the plants in some manner as co2 is heavier).
after that refrain from opening your room and if possible turn off any intake or exhaust fans(the ice will help keep things cool)
after like 2-3 days you should see a noticeable jump in budding or leaf production