I'm still rocking my original iPad. Haven't found any real need to update it. Based on my use case - added speed/memory isn't worth it. Only "worthwhile" feature for me would be the camera(s). But since my phone can do that - no rush.
Retina display? 4 times the speed? Lighter?
Let me guess, if Apple had added some "innovative" feature like "eye-scrolling" you would upgrade.....
Speed, display tech, battery life and design are pretty much the only ways smartphones/tablets upgrade these days.....gimmicky Samsung features don't count for me....neither do software features like Passbook that are available to older devices (or even ones that aren't like Siri).
This idea that phones need to be reinvented with innovative features every year is absurd.
The iPad 4 is a massive upgrade over the original iPad. If you don't feel that way, great - ultimately you use the device you feel works for your needs....but if the iPad 1 > iPad 4 isn't a substantial upgrade, I'm not aware of any recent tech (2010 - 2012) that provides a bigger upgrade.