In Watir you can use the set option to populate an input element, such as a text_field.  However, doing this will actually cause Watir to type out each character that you are inputting unless you run the script with a -f switch.  Why not trade all of this in and set the text_fields value with the text you want.  This results in a super stealthy input, without the need to pass -f.

Go from

ie.text_field(:id, /someField$/).set("My Custom Text")

to this:

ie.text_field(:id, /someField$/).value = "My Custom Text"

In addition, you should also realize that this really works best with a text_field.  However, if you want to be an alt-Watir coder you can stop using the clear option for radio buttons and checkboxes and pass false as a parameter to the set method.