They have been buying antminers for several months and announced that the revenue from bitcoin would make the company profitable. It's not clear how sustainable this is - given that mining ROI diminishes continually as difficulty increases. (as I understand it)

The stock may be a good speculative play on the success of cryptocurrencies over the medium and long term. The price does not track bitcoin closely, so probably not to be used as a short term derivative play on bitcoin price action.