To add to our collective knowledge, here is what I have learned re: ACV. The reason it is so good as a toner and a hair rinse (though use only occassionally on hair so you don't burn it out) is that it removes residue (soap, etc) and oils (sebum, etc) wherever it is applied.
I love using it as a toner, but I step it up a bit by adding a few drops of tea tree oil to a little pump dispenser I bought for like 99 cents at wal-mart filled with ACV. Just shake and pump out onto a cotton ball and wipe over your face after you wash. Both are excellent bacteria, fungus, etc. fighters and they seem to work symbiotically, the ACV clearing and opening up the pores for the tea tree to get into the skin even better. One bottle of tea tree and one bottle of ACV would lasts a very long time - my little pump doesn't need to be refilled more than every two to three months. Its such a cheap yet incredibly effective remedy. My boyfriend loves it too, but he will only apply in the mornings because he can't stand the smell of the tea tree at night. (A note of caution to anyone with sensitive skin - go slowly - use water in your mix so that your face can adjust to the acidity.)
One final note - Some ACV is really smelly when it dries while other ACV is not. Heinz I have found is the worst in this respect...I use the cheap generic brand provided by my local grocery store (here, Giant Eagle) - thus even further cost saving.