eBay style trading - I once bought a $100 trillion Zimbabwe dollar bill for Bitcoin. Think of the irony - using hyper-deflatory currency to buy hyper-inflatory currency :)
In bigger cities you can buy drinks and food with it in certain pubs/restaurants.
There are many more legitimate uses for Bitcoin, and even if most people hoard most of their stash, when you have to pay for something many tend to spend their Bitcoins if they have the possibility.
In the case of the price volatility for hoarding bitcoin while it rises, it underscores the deflationary nature of the currency - no economic value has been contributed by someone holding the BTC, but they've gotten richer regardless. Sitting around doing nothing with the BTC did not produce any economically valuable activity - it wasn't invested or used to finance starting that pizza place, for instance.
Oh, and the value frequently fluctuates double digit percentages in a day.