The point is $2bn is a significant amount of money. There's a LOT that can get done transaction-wise with that kind of money. It's the start of a mini-economy of its own... but only mini in comparison to current economies.
This is a big problem that does make it a toy currency. The slow exchange probably brings up the price. I expect, without much proof, that the USD:BTC ratio would be lower, at least short term, if you could exchange them easier.
$2b in circulation is pretty decent of course, but if you cannot convert those BTC to USD with ease then the valuation is flawed.
3 days is still a very long time compared to the 'real' currency exchanges.