Many reasons, IMO. It asks to save any word you may use that it doesn't recognize, (as I just did with IMO). Now it's automatically recognized. My daughter's name (Ali) would always be added as Ashli on Swype, no matter how many times I had used it.
It adds common punctuation/capitalization automatically , such as can't, won't, Calgary, and I. Secondary characters aren't long press, but simply touching the key and sweeping up or down, depending on keyboard location, etc. Plus, it's much more responsive.
It's free, give it a shot.
