Great questions!
So IDEX is somewhat "the middlemen" between the traders and the ethereum network?
IDEX acts as an arbiter, making sure that customers orders are broadcast in the correct order. In the medium term this will be fully decentralized and made into a protocol.
Are there any chance of corruption when the transaction gets on to IDEX before getting on ethereum network?
We cannot do anything without you first signing the order. The "corruption" this allows us to do doesn't make any sense for us do. For example we could not broadcast your order but there is no benefit for us to do that. Also because everything is on the blockchain if we were to do any funny business it would be incredibly easy to spot, resulting in us losing our customer base. We are not able to steal from you or rip you off and neither is a hacker.
Also, does IDEX works like EtherDelta in terms of accounts handling? We can just import our private keys then start trading? or there's a need to register first?[/size]
Same as etherdelta, connect your account and you are good to go. We support private keys (best UX, very fast!), MetaMask and Ledger. MetaMask and Ledger work great but are slow because you have to approve the orders on both devices whereas the private key executes right away.