To be fair, Samsung's built-in check-and-swap mechanism did look pretty similar to Apple's. The phone dictionary's proposed word hovers just above whatever you're typing just like it does in iOS. But the patent is phrased in pretty broad language and seems like it would apply to just about any kind of feature that suggests a better word than the one you're working on. If you're allowed to see both what you're typing and a suggestion at the same time, you're looking at a feature patented by Apple.
But is Samsung really the only manufacturer whose devices have that kind of autocorrect? We've come a long way from the days of T9, when phones could just swap in whatever they felt like right over what you were actually trying to text. I feel like the side by side comparison of what you're trying to say and what your phone thinks you want to say is pretty essential.
Maybe Apple just has a deep personal vendetta against this particular competitor. I'm sure there are plenty of patent overlaps between the iPhone and the various Motorola and HTC Android devices, yet Apple has spent about 100 million dollars battling Samsung alone. Seems awfully vicious, doesn't it? Especially considering they've largely been unsuccessful at keeping Samsung out of the phone and tablet business. Apple seems especially concerned with the Galaxy tab as a threat to the iPad, as many of those legal fees have gone towards trying to bar Samsung's new tablet from even being sold at all. Having failed to squash the Galaxy on the basis of design patents--judges ruled that you can't, in fact, copyright rectangles--Apple is now rearming themselves with utility patents. If I had to guess, I'd say that the judges will probably assert that you can't really copyright autocorrect, either. Whether they like it or not, Apple is going to have to deal with Samsung as a tablet competitor, even if they take a hefty swipe at the enemy's legal budget as they go forth.