They actually aren't that great. None of the shorts is labeled, so you have to sit there and wait to have the little description bar go by. Also the opening animation is annoyingly long and unskippable
Pardon me for a moment, but i've been wondering this for some time now and this seems to be a good place to ask, what are these short films and are they necessary to see in order to understand The Matrix Reloaded?
Yes they are short films and presumably no they aren't required viewing in order to understand The Matrix Reloaded (although apparently The Final Flight of the Osiris does set in motion the antecedent events to the film)
However (in my opinion) they are very cool looking and informative additional stories set in the Matrix universe, check out four (of nine) shorts online at http://www.intothematrix.com/.
Renaissance is the prequel to the Matrix story, but Osiris is a direct prequel to Reloaded; although you don't NEED to see it to understand the new movie.
If you see Osiris, and play the Matrix video game, it'll give you little glimpses of things that were happening at the same time as the movie. They aren't required, but they are little bonuses to the story.
One of the Animatrix episode has a boy who is saved by Neo. This character appears in Reloaded with Neo making a comment on how he saved the kid. None of the animes is a must to understand the Reloaded, but 4 episodes help round out the Matrix story with Osiris and the boy episode having direct references in RELOADED.
Animatrix is an interesting collection of many different styles due to the different animators. Osiris is the best (only all CGI in the group) followed by the Peter Chung episode, which I cannot remember the title to. I just wished the episodes were longer. It left me hungry for more.