I think it really depends of what you want for a video. If you are doing somethin simple (like a familiy video) I think it is better to use editors like
For Windows: Magix Video Deluxe, it's 10 times better than Windows Movie Maker since it has some cool extra effects and it is really easy to use.
For Mac OSX: iMovie HD 6. Better than the "new" version of iMovie that is included in iLife 08, since it's more intuitive.
In case you want to do something more professional:
For Windows: Adobe Premier
For Mac OSX: Final Cut Pro
Both have some similar features and both require some extra experience and can have some restrictions with formats but the outcome is really fascinating.