A very good point, SSC. Being fairly new to working in aviation, and not having filed a flight plan as a pilot, I'm only just seeing the tip of the iceberg with the problems flight plans can cause if they're not filled in correctly. I've seen the wrong registration turn up for an aircraft because the pilot's handwriting couldn't be read... I've seen flight plans arrive with us instead of the real destination because someone has typed in the wrong ICAO code... etc etc. Oh, and frequently they are filed late! They're a fantastic safety net when used correctly... DO SO.
And if your handwriting is less than neat, ask a mate to help.