I have a paragraph of text on the stage that looks good (Helvetica Neue, Ultralight), but when I play the movie it looks much thinner and really bad. Why does the text on the stage not match the movie?
If it is static text and you are using a dynamic textfield, try changing it to a static textfield. Also, you may want to try different anti-aliasing settings for the textfield (via the properties panel). If you are doing anything to filter the text, such as applying a drop shadow, this can also impact the appearance. If all else fails, try a different font.