Our experience with the scenario you describe is as follows.
1. You have a template with an iFrame somewhere else on your page that is tied to this same model.
2. When you type a character - the model detects changes, the template says “Ooh - I saw changes and need to let my iFrame know about it” and focus is grabbed by the template.
3. Having lost focus on your text box, you do somthing like hit the back-space and your browser takes you back a page. ACK!
So tie the template to another model (even if it sourcing exactly the same data from the same objects)…
And yes - Text Fields should work with the code above.
