Apple has added a 128GB iPad 4 to it’s lineup (at least within a week), but it is $799 for WIFI and $929 for 4G, so they are charging a premium for more memory instead of staying the same price as they get bigger.
Starting to get to be the right size, especially for video and audio, though I could still use bigger. I keep most of my music in Apple Uncompressed AAC, and it is huge, and I am constantly fighting it being full.