Recently I struggled over another problem with the TextField where the textWidth / width was not calculated right.

On the screenshot you can see textfields stacked from the left to the right corresponding to the width of the textfield. If you look closely to the borders you see that the leading and tailing spaces around the words are not equal at all. Especially at the word “Newsletter” the tailing space too small. The texfield was setup like this;

label.autoSize = TextFieldAutoSize.LEFT;
label.wordWrap = false;
label.multiline = false;
label.antiAliasType = AntiAliasType.ADVANCED;
label.gridFitType = GridFitType.PIXEL;
label.embedFonts = true;
label.border = true;
var test:TextFormat = new TextFormat();
test.kerning = true;
test.font = "Futura";
label.setTextFormat( test );

The solution:

It seems that this is a flash bug and you can get over this by changing the GridFitType.PIXEL to GridFitType.SUBPIXEL.
The resulting textfields look like this;