What were you expecting? The differences were discussed here a lot and advise was given in regards to whether one should do the upgrade.
I assume you had an iPad 3?
In order to see a difference, you need to find a game where the iPad 3 was not able to update the screen quickly enough. In theory, for these games, the iPad 4 should be able to do a better job than the iPad 3.
If you have goodreader, open up a PDF scanned at 300 dpi. On the iPad 3, these can be very slow to update the screen and you get this checkboard pattern on the screen if you scroll the pages too fast. I hope the iPad 4 will do better at this...though, for me, this alone is not enough reason for me to update.
The charging connector is really nice.
Supposedly, wifi is faster...but....and supposedly it has better battery life than the 3.