Bitcoin is in use right now transferring money around the globe. If I buy 100$ worth of bitcoin (0.478 bitcoin at current prices) and immediately use it to purchase anything, it has served its purpose as a value transfer medium. This is regardless of tomorrow or yesterday's price. It is this efficacy that people pay for when they buy bitcoins.
Bitcoin was not designed as a storage or investment medium it was designed to facilitate the transfer of value. As long as it performs that function it will continue to defy the misplaced expectations of those who refuse to go to the effort of understanding it.