There are plenty of keyboard "improvement" apps on the Marketplace meant to improve Android's typing experience. Two reasons: because the Android soft-keyboard sucks, and because Android is open enough that they can. ThickButtons is a pretty good evolution of this.
How it works is that ThickButtons visibly enlarges the keys that the phone predicts you'll type next, so if you're typing the word "Annoying" and you get to the "o", it'll enlarge the letter "Y" (among other letters it thinks you can possibly hit next). The iPhone actually does this invisibly, but ThickButtons does this... visibly.
Lifehacker says that on the whole the enlargement is good, but can be distracting if it doesn't enlarge the letter they were looking for. Our problem with it is that it's great for beginners and common words, but if you ever want to get really good at typing on Android, this seems like a crutch you'll have to throw away eventually. By always having to look at the enlarged keys, you're limiting yourself from touch typing on the phone - which is the same premise people use to learn touch typing on regular keyboards (not looking at the keys). [ThickButtons via Lifehacker]