I used Swype (and loved it) until the first trial time expired. Then learned through the forum that it was "unavailable" until "whenever."

Crap!
I wanted a slide-type keyboard and didn't want to deal with another sudden expiration, so I downloaded SlideIt and ShapeWriter and alternated between the two ... until ShapeWriter won out.
No having to "curly Q" on double letters ... the word LOOK is entered by sliding over L-O-K. Rarely do I have to tap out a word that's in the program dictionary.
New words can be entered to the user dictionary on the fly, though Swype may have the same feature - haven't used it in months so I don't remember.
It took a lot of searching to find the underscore "_" key, which is buried under the "@" key (lower left of keyboard). Pressing the "@" key brings up a sub menu, above the keyboard, that can be scrolled to the right.
ShapeWriter and Handcent are my favorite texting tools.