There are at least a dozen third-party keyboards that can be used on the HTC EVO 4G instead of the preinstalled one (designated as "Touch Input" on the input method menu). Installing many keyboards and switching between them is very easy—tutorial here—and while it's fun to do that, you'll eventually find a favorite and stick with it.
In addition to SwiftKey, Graffiti, and the Droid X's multitouch keyboard, I've used Swype, ThickButtons, Smart Keyboard, Better Keyboard, AnySoftKeyboard, TouchPal, and the stock Froyo keyboard on my EVO. My favorite, and the one I use about 95% of the time, is Swype.
Other than its amazing accuracy, speed, and the fact that I can use it with just one hand (must-have feature for a new mom), what I like about Swype is that you can also tap on it like a regular keyboard if you want/need to. You don't always have to swipe the keys.
It's standard to tap the keys to enter an unknown word that Swype then learns, but you can also just tap on the keys normally whenever you want. For example, sometimes I find it easier to tap rather than swipe in Twitter because of all the abbreviations necessary to stay within the 140-character limit. This "dual mode" usage makes Swype very versatile and is a best-of-both-worlds keyboard for me. It doesn't have a voice-to-text button yet, but I wouldn't use it if it did so its absence doesn't bother me.
Which keyboard do you use on your EVO? What makes it better than the preloaded HTC one and/or any other keyboards you've tried?