The first film broke new ground for it's special effects, and was incredibly popular (though it was a bit loose with small things like the second law of thermodynamics). The new films are eagerly awaited, and should prove to be excellent.
In the summer, they will be releasing The Animatrix on DVD, this looks set to fly off the shelves.
At the time of writing, it looks like the UK release date will be the 23rd May, one of the last on the list. Poor ol' Japan has 7th June though
Update from 2008: Looking back... 'excellent' and 'matrix sequels'. Don't see those phrases in proximity these days.