That's where the protocol confusion freezes most discussions. There isn't a native currency per-se. There are IOUs and XRP. The "pitch" is that XRP aren't currentcy, but transaction credits. Currently I'm allowed to do 75 million transactions, but my cost for transactions will go up as servers take load and try to discurrage transactions (by raising the credit cost).
But after I burn through my 75 million transactions, I can "buy" more credits. This is why the credits cant shake the currency tag. Since they are buyable, they are defacto currency. Hence the targe of the the gas and firestorm.
Well, then don't call them currency but asset - anyways, XRP are the only thing in Ripple that can be transferred without issuing trust atm. and they are also intended to be "path shorteners" by allowing people to pice their IOUs against XRP. I'll have to look at market orders too to make an educated statement, but if I look at the trust graphs for USD and BTC alone, Ripple is heavily dominated by Bitstamp at the moment. It depends on market orders, but I guess BTC.Bitstamp and USD.Bitstamp are also useful for direct trade without XRP as intermediate already as well (e.g. against CNY from various issuers).
Once I finish my stuff, I might publish some of it - which should give ppl. a better estimate of what is going on in "Rippleland" (e.g. I have seen VERY different estimates about how many XRP are now dispersed amongst users). I'm not too sure about the format though and how to actually profit from it (I invest already quite some time), maybe charge some BTC amounts for a paper on coindl.