The mentioned app is ok at best for a minimal iphone app. To answe your question, Anirban, it lets you browse code, view issues and changesets. But beyond that is useless. As for an iPad, it is simply not an iPad app.
Adding line numbers to the code browsing would be sweet.
If there was an iPad/iPhone app built by Atlassian, you know it would be slick. An app made by a third party will never be as slick as one by the owner of the service.
My friend and I recently created an app called BugBranch that lets you view/edit BitBucket issues. It also supports Redmine, JIRA, Trac, and GitHub issues. Even lets you check out non-BitBucket mercurial and git repositories.