Everyone who goes to Bayeux knows about the Bayeux Tapestry, but let me say this: Don't believe the hype.
Yes, it's impressive that the tapestry has lasted for so long. Yes, it's impressive that it's enormously long in size. However, the presentation was pretty poor. You first walk through corridors with a mock tapestry that tells the story in English and explains what's going on. Definitely helpful, but the presentation seemed second rate. Also, the "movie" that was shown was very dated and didn't seem very professional.
However, even with all this, you should still go because the tapestry is such a famous artifact. Keep your expectations low, and if you're dying to do something else, don't feel bad about skipping the tapestry.