When you trade in the DEX (BitShares Decentralised Exchange) you are in control of your funds. 
I mean that you own the wallet where the different token traded are stored at any time.  Nobody could hack the DEX and steal your funds, the only way is to hack your personal computer and get the private key AND your password.

Technically, you can have as many fiat gateways in BitShares Decentralized Exchange as you want. Another problem is to find a company that is able to coordinate engineers, accountants and lawyers to start a real-world business in a particular country.

Open Ledger used the BitShares Decentralised Exchange to build its own. As the company didin't make any change at the basic graphical interface at the moment, both (desktop wallet and openledger browser wallet) look the same. Just like others did : https://secure.freedomledger.com/#/

BitShares allows you to use its own plateform to create yours relatively quickly. Then you can tweak whatever you like, add your own assets and benefit for the market trading them. It's probable that you'll see more and more trading platform using BitShares. 

Besides the benefits of having all the front end and back end already coded and free, all plateform shares their assets and orders book. So when you launch your new trading platform, you already have volume, you just need to add your assets and promote them.

Open Ledger did create a lot of tradable UIA on the BitShares plaform that allow users to trade ETH, LISK, WAVE, HEAT, DGD, STEEM, DOGE, ... You can see these assset by the name open.ETH, open. DOGE, ... 

You can download the desktop version or use Open Ledger, at the moment their is not a lot of difference but they will come. 

The claim is real BitShares is a fully decentralised exchange and so OpenLedger.  The assets created on the plateform, are more secure than assets you can have on centralised platform but still depend on their creators. 
That said, Bitshares have plenty of assets that are independent and then completely secure and decentralised. See BitUSD, BitCNY, BitGOLD, BitSILVER, BitOIL, Bit...