I think that they are an investment.
BTC cant stay at ~100$ forever if its going to be "successful".
With only 21 million coins, market liquidity won't be possible with only $2.1billion money stock.
The good thing is that Bitcoins ROI time is shorter than traditional investment methods.
Its still a gamble, and with all big rewards, comes big risks - just as it has been like at every step of Bitcoins existence.
The problem is that BTC price is not rising in relation to difficulty increases as it should be.
The US gov has gone out of it's way to make it harder to get $USD into BTC exchanges, and there are periodic rapid BTC sell offs driving the price back down, when it should be rising.