Is there a reason I should start using these currencies? Aside from trading currencies to make a few bucks?
If you look at Greece where savings accounts got a haircut and ATM withdrawals were frozen, or Venezuela where staple commodities and health care are now in cases only available for Bitcoin due to their currency crisis, the robustness of it is apparent.
It does have technical risks, but those are simple and easily understood. Personally, I am excited about ethereum, which turns the global mining network into a Turing complete engine for arbiterless smart contracts, where payment is built into the process mechanically rather than obliged legally and bolted on by trust like in a traditional contract.
Until the owners (and there are owners) of Ethereum don't like the outcome of a particular contract and roll everything back for their profit/gain.
If segwit becomes merged, it suffer the exact same central authority criticism, but the divided community will likely cause a shock selloff.
The primary draw to cryptocurrencies as commodities is the mere fact that they exist. It's pretty much a universal constant that a speculative market will arise around anything that can be traded.
Blockchains are neither fast nor cheap; their value is trustlessness, not performance. The SWIFT network handled 15 million transfers per day in 2015 [1], Bitcoin's current maximum is around 600k per day/~7 transactions per second. That being said, the Bitcoin-limit is self-imposed (1MB per block), but even so the security of the network weakens as storage requirements for nodes increase, so some limit is required, in my opinion.
The value of crypto currencies is in the decentralized/trustless medium of exchange. I think, in the end, we will use various clearing protocols on top of Bitcoin, in order to circumvent the slow on-Blockchain settlement (just like VISA handles consumer-to-merchant transactions instead of SWIFT). It's very much like gold: perfect as a store of value, but relatively cumbersome to transfer from person to person.
[1] https://en.wikipedia.org/wiki/Society_for_Worldwide_Interban...
At least, that hope is why I myself dabble. I also think it's why there's so much enterprise investment in ethereum.
Bitcoin is available anywhere the internet is available (so it cannot be censored), and has a relatively low, flat transaction fee. This gives it utility in money transfers. It is also secured with cryptography and anonymous (yet not completely un-traceable), giving it utility for storing value.