Here are my 7 reasons why you should buy bitshares:
1) Like Bitcoin, it is an implementation of the Blockchain technology: A decentralized ledger.
2) DPoS. DPoS doesn't waste money through inflation in order to secure the network. DPoS > PoW.
3) BitUSD. BitUSD provides stability and solves bitcoin's problem where merchants dont want to hold it due to price volatility. It even provides yield!
4) Paid Delegates. Bitshares has the ability to fund its own development through paid delegates. This allows Bitshares holders, by majority vote, to elect someone to be paid (through inflation) to do whatever we are hiring them for. This gives us the ability to hire developers to improve Bitshares. It could even result in us hiring many developers away from other projects where they wouldn't get paid, poaching the talent from any competition. Not: Inflation caused by this is maxed at a rate lower than bitcoin inflation. Realistically it will likely be more like 2% or so, which is quite low.
5) Speed. 10 second transaction times (or even lower) with DPoS is greatly superior to bitcoin's 10 minute transaction speed or Litecoin's 1 minute.
6) BitAsset Exchange. Other BitAssets like bitGLD are useful to allow exposure to whatever price volatility you want. Bitshares is an exchange, not just a currency. Additionally, trading fees are used to burn shares of BTSX, reducing the overall supply (counteracting dilution!)
7) Other features. Anonymity (TITAN), and Upcoming features such as VOTE, DNS, Turing complete scripting.