You can launch pretty much any iPhone app on the iPad. If it’s not a universal app, it’ll look all pixelated and ugly and you’ll wonder why the developer hasn’t gotten around to making an iPad version of the app. Maybe the developer’s happy with just an iPhone app. Maybe they’ll rush an iPad app into the store and it won’t take full advantage of the iPad’s capabilities. Or, maybe they’ll create an app that’s worth the wait. Tweetbot for iPad is the last one.