One option, http://www.gimpsta.com/themer/ allows you to theme the HTC_IME keyboard, and the theme can make it match stock (or fairly close). You won't need to be rooted to use this, just need to have the "install from non-market sources" be not checked.
After it's install, just go to settings > keyboard and make sure it's checked (and you can change any of its settings at that point, related to auto-correct and the like) and then long-press on a input area (I usually just hit the search key on the phone) and choose input method > htc_ime keyboard.
After it's install, just go to settings > keyboard and make sure it's checked (and you can change any of its settings at that point, related to auto-correct and the like) and then long-press on a input area (I usually just hit the search key on the phone) and choose input method > htc_ime keyboard.