Ah, I was using System Wait actions before moving the Textbox, which seems to be what screwed it up, though I don't know why.
On the PC anyway, the On Text Changed works as I expect it to, and triggers whenever a character is entered or deleted. Thats fine, I was expecting to check for a newline, but the OnTextChanged does not trigger when I hit enter. I'm a little unclear on how things are supposed to work on a smartphone. I'm using OnKeyPressed for now untill I get a phone and test it.
Also, is there any way to detect whether a keyboard is attached at all? I figure I need to build a gamepad friendly text entry box if the keyboard is missing.