Wow, an excellent thread with thoughtful responses in bitcoin discussion.  That's a rarity.

Op, you made some very good arguments even if I don't fully understand some of the technical aspects of what you wrote.  What I found most interesting was your explanation of why proof of stake isn't as good as pow, because I like some of the pos coins and use a few for staking.  I don't think any of them have a fatal flaw, but I concede that their design probably isn't as secure as pow coins. 

It was *supposed* to be a currency, but it isn't really being used for that so much as either a store of value or an investment, whatever the difference is there.  In fact I've always thought bitcoin was a crappy currency for a whole host of reasons, but it certainly can be used as one.  It isn't even that great a store of value since it has volatility that would make even penny stock traders nauseous.