Oddly enough I actually thumb typed quite well on the 5500. Something to do with the combination of small round well spaced buttons and holding the device in landscape mode

Recently I was introduced to T9 on a friends phone and I wonder how that would be on a Lenovo MID, for example, where you have a large array of text input keys on the right panel..
http://www.pocketables.net/2008/01/lenovo-mid-and.html

It does seem that we need to find a better way of inputting text on a handheld. Simply mimicking a full size layout on a MID may not necessarily be the best way.