One more reason not to use octane booster:
Usually, the boost is achieved with MMT (manganese) -- the heavy metal replacement for lead -- you can read it in the ingredients list. Most car manufacturers will tell you that MMT is not good for you car -- like lead, it will coat sparkplugs and foul emissions equipment. One of the requirements for top tier fuel is to be MMT free.
Side notes: MMT is no longer used in the USA to increase octane, it is now banned. Canada attempted to ban its use in 1997, but was sued under NAFTA buy the company that supplies most of it (Ethyl Corp.).
Another side note: MMT, like lead, is suspected of causing neurological issues in children. I do not preach to anybody what gas they should buy, and I don't generally drive across town to avoid it, but I'll buy MMT free fuel whenever I have a choice -- as a father of a child with neurological issues, I think it's only right (for me, anyways). End soapbox!