I never upgraded from the first generation iPad to the second. I thought the second generation was more of a generation 1.5. But I was sorely tempted by the upcoming 3G iPad. Indeed, the improved cameras and retina display were what swung it for me, and yesterday I received my shiny new gadget. These are my first observations.
First, that retina display. It's astounding. But not so much for photographs as for text. Where on my 1G iPad I had to do quite a bit of zooming to read fine print, the text is spectacularly sharp and clear. And when I return to my MacBook display, it seems pretty poor by comparison ( but not so my very old Sony Vaio Ubuntu laptop, which has tiny pixels).
Second, the cameras. Friends tell me that the images captured are significantly better. Frankly, using the iPad as a camera is likely to be something of a minority activity (for me at least), but it makes it possible to use FaceTime.
Third, the battery. The
iFixit guys show that the interior of the device is mostly filled with battery, about twice the capacity of the second generation model. It does seem to take longer to charge, but the extra battery capacity seems to be needed by the screen, so battery life isn't improved.
Fourth, the 3G model seems much snappier than the 1G model.
So far, happy with the upgrade from 1G to 3G.