I'm only a little disappointed so far in that I only see work in the intermediaries (coinbase), nothing really revolutionary like Silk Road. Something that makes use of its properties that conventional currency cannot provide. While enforced monetary scarcity is the main thing going for Bitcoin, I would like to see more "killer apps" providing an underlying value in order to distinguish it more clearly from xyz scamcoins.
Sure, being able to buy gift cards for Burger King with Bitcoins in the US is nice. But let's not kid ourselves, it's only convenient if you already posess Bitcoins and happen to run out of USD. An unlikely scenario.
Agreed regarding the network effect... No alt has brought anything interesting to the table yet, with the possible exception of ppcoin (though any benefits wouldn't materialize for years if ever (eg, when mining energy costs start to have a big effect on transaction costs, which is debatable anyway)). I think if bitcoin continues to entrench itself as the "local currency of the internet", cypher will be right that it'll take something wholly different than crypto-currency to displace it. Not sure we're at a sufficient level of entrenchment quite yet, though.
Regarding the killer app notion, yeah, store-of-value/scarcity is one. Frictionless transacting over any distance and transaction-security (ie, not exposing sensitive info with every electronic transaction) are the others. Does it need anything else? Those are huge.