for those who have released universal apps, do they appear in both iphone and ipad stores at the same time ?, if so, is it just automatic by making universal or something is needed to be done for that ? thanks!
You don't have to do anything special. A submitted universal build will be automatically detected as such by itunes connect. In search results, a universal app will show up in both the iPad and iPhone/iPod sections of itunes and iPad appstore, with a "+" next to it. On the iPhone, there doesn't seem to be any special indicator, so you're on your own to call attention to your app being iPad enhanced.
