the only worthwhile upgrade for the iPad 4, and it's a big one, is the A6X processor. for any people who owned an iPad 2 and then an iPad 3, and they played graphics intensive games, they know the inadequacies of the A5X. games like Metal Storm hiccuped, stuttered, and the overall game play was inferior to playing the same game on the iPad 2. the Retina screen is a beast, and the A5X just couldn't handle the beast when you took the iPad beyond its normal paces.
for anyone who does not yet own an iPad or owns an older model than the iPad 3, getting the iPad 4 is a no brainer. for anyone who already has an iPad 3, taking a resale hit to get the iPad 4 may not be worth it. for anyone who has an iPad 3 and they fall within Apple's unofficial 30 day exchange period (such as myself), upgrading to the iPad 4 is a no brainer. i just returned mine tonight at the Ardmore, PA (Suburban Square) Apple Store - they took it back without any problem.
the Lightening connector is an annoyance for some and a convenience for other. i won't comment on the port change, since it all depends on whether or not you have an iPhone 5.
the Facetime HD camera is a nice whistle or bell, however you want to call it. not needed really, but nice to have. i can't complain that i'll get to see my girlfriend in HD on my business trips, although it'll make it more noticeable when she washes off her makeup at night (don't tell her i said that).
i can't comment on the 2x increased wifi speeds, as for the internet speeds i get with FiOS the main bottleneck will be the connection itself, not my wireless connection from my iPad to my router.
it really all comes down to the A6X which will be a godsend for the iPad Retina when it tries to handle the Retina and push video game graphics rending on that beautiful display. i welcome the upgrade, the only downside to returning my iPad 3 tonight is that i have to wait a month to get the iPad 4. it'll be worth it though...
good riddance A5X