The token is useful in that it is used to convert between others in the network. It is the plug in that connects your token to the algorithmic price balancing formula. It is relatively stable to other tokens in that it’s liquidity is centered in one location, rather than across various exchanges, and its price moves predictably according to buys and sells, rather than by matching parties in an exchange at their requested prices. You see some analysis of this relative stability here: https://blog.bancor.network/bnt-the-first-smart-token-is-born-22a0f3a38bf2