When talking about money, people usually say something like “money has no or very little direct use value and is only useful as a medium of exchange”. For instance, you value your silver spoon for its immediate use during the dinner, but the dollar bills do not have any value in themselves — they are useful only when there are other people around who are willing to trade some of their stuff for these bills.
Generally, people perceive Bitcoin as currency which makes them think that the same arguments about its value apply. That is, in itself Bitcoin is some digital dust which can only have value as a monetary instrument. But that’s not the case at all.
Bitcoin network has very interesting properties that allow you to use it not only as a currency. For example, the block chain (decentralized transaction history) is designed to be extremely hard to forge and very easy to verify. This, with some crypto features, allows it to be used for secure time-stamping, proving ownership of tangible property, decentralized DNS and new ways to sign contracts without having to fully trust any one party. Some of these things are already possible using existing software, some require already planned and compatible modifications.
These things are not possible with any commodity-based currency (metals or paper bills), but possible and very easy to use with Bitcoin. Just think about it: in case of a contract dispute, you can provably verify the details of some contractual agreement in a matter of seconds across the ocean to anyone, without sending paper documents with ink signatures by mail. The only requirement for this is to leave a trace of your contract up front in the Bitcoin block chain by making a small transaction back and forth to an address, uniquely derived from the document contents. It costs almost nothing, can be done in a minute and the trace cannot be forged or erased by anyone in the entire world.
Edit: rephrased a couple of sentences according to the comments on HN.