In terms of buying bitcoins; it sounds like it's just about the same user experience, maybe a little more complicated. I guess I'll stick to mtgox.
It will be a distributed exchange, and therefore much more resistant to DDoS or government shutdowns than Mt Gox.
And what need have I for IOUs when I can just as easily pay/receive real value in the form of bitcoins? It seems like an IOU is only useful when you're broke, or you've mismanaged your cash flows and need to borrow. And in that case, why not just borrow some bitcoins directly?
Traditional electronic fiat currencies are IOUs too, you have to trust that your bank will redeem your balance in real dollars. An electronic ledger is no more than a record, it cannot enforce settlement in a real world currency. When you trade BTC for USD on Mt Gox you are effectively trading Mt Gox issued BTC IOUs for Mt Gox issued USD IOUs.
One of the interesting things about Ripple is that it allows you to specify explicit trust lines. All nodes you can reach through these lines can pay you and you can pay them, and you don't need any banks or governments to do it. Each party settles with his or her direct neighbours periodically, in whatever form is convenient. As adoption increases, you'd have to settle less and less frequently, because more and more companies would accept payment through Ripple.
I expect Ripple to become more reliable, resilient, anonymous and liquid than Mt Gox.
Are you using ripple for any kind of commerce / financial activity? What for?
Just playing around with it for now. If I'm going to buy any new BTC, it's likely going to be through Ripple. I won't hold large amounts of XRP or IOUs in the Ripple system until after the code is open sourced, gateways have proven their creditworthiness and many others than OpenCoin are running validators.