Tron Legacy is just ok. 3D and IMAX don't bring anything special to the experience. But if you liked the original you'll probably like the sequel for the same reasons. Save yourself the money and just see the regular version.
Following in the footsteps of the novel the movie is a more mature experience that may not be appropriate for some young children. The film is well acted, though after seven films staring the who's who of British thespians its not surprising that the stars give good performances. The only bad thing about the film is that we have to wait until the summer to see the rest of it.