- The IOU thing is idiotic. Unless you want to create a massive debt apparatus
All bitcoin exchange deposits are IOUs, there's no way to get around that unless you never trade bitcoins on an exchange. IOUs are debt, but its a very simple form of debt. Much simpler than the case of ponzi-type "fractional debt", unless a gateway is operating fractionally and issuing more IOUs than it has in actual deposits. Thankfully, on ripple we can see exactly how many IOUs a gateway is issuing, this is one of the primary reasons I like ripple so much (eg current bitstamp gateway capitalization is $272,957 USD and 2,583 BTC).
- You can backup your wallet to a file, but nowhere can you import it
You're right, one of the settings in the web client is to fetch your wallet blob from "local browser", which uses the HTML5 localStorage API. But there should be a more explicit and usable way to select a wallet file. Hopefully they'll implement that soon.
- It's only accesible on one website DDOS, Bitcoin is on a desktop/Websites/Mobile
You can run a local copy of the web client. You can download the ripple-client from github to do this.
- Your not really in control, with Bitcoins you are
Sometimes it appears that way because the web client is hosted at ripple.com. So its easy to confuse ripple.com for a centralized payment system, similar to how its easy for people to confuse the blockchain.info web client for the actual bitcoin blockchain. But there is work proceeding on a gtk client (uses GTK as a GUI framework, instead of QT), and now that the rippled server is open-source, people can also run their own ripple servers.