When you go to purchase, you will get a message to say you have already purchased the app and it will download and install, as long as you are using the same account.
The universal thing, its the + sign isnt it for both the ipad and phone. Some of my old angry birds games that i purchased before the ipad even came out had to be purchased again for the ipad, i could still use the old games but not as good as the dedicated ipad HD versions
It is Words With Friends HD. Which doesn't.t seem to be offered for the iphone..so bought the Words with Friensd thinking it would pick up the game I have started with Hd but it did not nd I think I am charged for it ...ugh.