The DLP rainbow effect is caused by the way the DLP chip works with the color wheel. The wheel/bulb shine light on the DLP mirrors very fast in three alternating colors. If your eyes are fast enough, or if you do certain things like shift your eyes back and forth across the screen quickly or wave your fingers between your eyes and the screen, you will see rainbow trails. Many people don't notice it, but many people do. And if you do notice it, it can be distracting as hell.
LCD and LCoS rear projection TVs don't have the rainbow effect, but also require the pricey bulb changes.
And yeah Dawn...Panasonic is one of, if not the best plasma manufacturer.