The "entrenched" digital immigrant (and native?).

Marc Prensky's term for a late adopter of technology, as opposed to one who has known nothing different, is "digital immigrant".
Two years back we were using this concept to explain the differences between "digital natives" and "digital immigrants". Many parallels between new immigrant behaviour and that of someone who had learned how to use computers, and thus slowly change their ways of working, could be drawn.
But there is another layer to this.
Probably occurring more often in the immigrant than the native, there is a "just enough knowledge and no more" approach as well. There are those who have become entrenched in some Word, some spreadsheets, an on-board mail client, Skype and the ever present powerpoint, and that is it. There is not the wish to move further than this.
"Good enough for what I want to do", they might say.
How common is the entrenched digital user? What might move them on to consider other digital computer and collaborative tools?