I'm considering buying an iPad 2. I already have an iPod Touch and was wondering if there is a way to upgrade apps, either for free or pay the difference, that I have already purchased in order to get the iPad specific version, or do I have to rebuy anything that I would want on the iPad? I know it can run iPhone apps, I'm just looking at the apps that have specific ones for each device.
The best answer is that it depends:
There is no way currently to 'upgrade' to the better version for a discount between devices. So to answer your question, you would have to rebuy anything you want on your iPad (thats specifically iPad based) that wasn't provided for free from the developer in an upgrade to the app (where the developer made the app universal with an update).