Just downloaded the first version of Twitter for iPad (iTunes link) and trying it out. On first glance, love the clean, properly-sized UI. Try pinch/zoom on a tweet to see more info. Pinch again to close. Swipe down with two fingers to see a thread. The “write a tweet” view overlaps a bit much for my preference, but otherwise, really liking it so far. If you’ve had the iPhone version, delete it from your iPad, then reinstall from the App store.