The "Wham"'s outline looks pixellated... when I have to highlight text, I'll use this technique:
Put a layer underneath it Select the text Expand the selection by 2-3 pixels Fill the selected area on the layer underneath with the highlight color Release the selection Run a gaussian blur at 3 pixels on the underlayer Merge the text onto the underlayer.
That way, the highlight's edges retain enough alpha to blend seamlessly with the background.