Nice little app! If I was being picky I'd say it's an odd mix of fonts across the interface, but otherwise looks pretty nice
However… this is an app you're asking people to entrust their MtGox login details to. What assurances can you give us about security? I assume MtGox make you use a secure connection to the server, so I hope that isn't an issue, but what about the app itself? Does it store the login credentials you give it - if so, does it use its own store or use the Keychain? As this appears to be a closed-source application, how can I be sure that this application isn't secretly a trojan capturing account details?
Understand that I'm not trying to criticise you, but that you will need to have (good) answers to security questions. I wouldn't trust a third-party website with my MtGox credentials, so why would I trust an application with them?
I am glad to answer these questions. MtGox does require a https connection, and the login credentials are stored, and I am currently working on an update (t.b.r. later today) that stores the credentials in the keychain. They are currently stored in a file hidden deep in the system. Security is a very important aspect of my application. And if it were a trojan, why would I bring so much attention to the identity of the developer, if it were discovered that it is a trojan, then they would trace my ip from either the host of my website or from this website, and I could be in some legal trouble.