I don't utilize Bitcoin as an investment vehicle. Personally I feel it is better suited for use as a medium of exchanging value. In my business we accept Bitcoin for various reasons including that it saves us about 3% over credit cards and when people purchase some of our most expensive products depending on what else they buy it's possible that 3% actually exceeds the profit margins. Profit margins on computers (one of the things we sell) are very very low particularly at the low end of the spectrum. Another 3% is great to get out of it. Now this particular sale at the low end doesn't double in value, but that money also wasn't invested for a year, and the most expensive parts are often bought and stored for fairly short intervals. So Bitcoin for me is readily available for me to spend without going through a middlemen or paying a premium (though I have twice purchased $500-1000 in BTC through others in order to pay bills).
While Bitcoin does go up over the long term its generally pretty stable for long lengths of time. It can go down too, but generally still goes up over the long haul. Long haul though can be two years to return to previously values. When I make an investment I want to be reasonably certain that whatever I invest in will double or triple in value over the course of a year or so (if that is the length of the investment). Bitcoin doesn't really do that unless you give it greater periods of time or otherwise get lucky. Now I have "made money" off having Bitcoin, but that wasn't the objective. I've also lost money. Over the long run I've gained more than I lost so it's no big deal, but I still think it is a terrible investment vehicle given other options available. Some people have gotten lucky off Bitcoin, but that doesn't make it in and of itself a smart investment vehicle. I think using it as an investment vehicle is more like gambling than investing.
Investing in Bitcoin (a smart investment) to me would be investing in vending machines and placing a mark up such that you can reasonable ensure the profit margins provide a return on that investment. The other thing you can potentially do is if you get other businesses to accept Bitcoin you might be able to utilize that to reduce your investment costs (slightly). If you get Bitcoin at value rather than at a premium through an exchange you'll make more money when someone goes to buy it. As a vending machine owner (I'm not currently) I'd be on top of working toward getting more businesses to accept Bitcoin and maybe even paying businesses to do so... that said I am trying to promote Bitcoin simply for all it's various benefits not even including making more money. It's decentralized and puts users in control rather than a government. You don't have to ask government for permission to send that money like you indirectly do with that wire transfer at your bank. As some people in our community have experienced the banks and government have attempted to stamp out Bitcoin and competition through shutting down Bitcoin business owners bank accounts. While the government can still make a Bitcoin transfer illegal they actually have to do something through violent action to stop you from doing it. That's a lot more expensive for a government to do than simply making banks shut off users access to the banking system. So spreading Bitcoin far and wide actually takes away some of the control government has on all of us.