I'm curious why they released a new full-size iPad after only 6-8 months of the iPad 3 (I refuse to call it the "new iPad" since it's no longer new or the "iPad third generation" since that's silly). Apple used to have yearly product cycles, and in no world can I see Apple only giving 6-8 months on premiere item. In fact, if you look at their new line-up graphic, they are still selling the iPad 2, but there is no mention of the iPad 3. In addition, they only referenced the iPad 3 a few times in the presentation, but there were many mentions of the iPad 2. It's like they wanted us to forget about the iPad 3. Very strange.
I can only think of two reasons why the iPad 4 would be released -- either they had some supplier issues with the existing iPad 3 (quality control, costs, etc.) or they wanted to make minor changes to counter an upcoming Google 10" or Microsoft Surface tablet. It looks like the only meaningful change between the iPad 3 and the iPad 4 is an upgraded processor. If so, why announce an entirely new product after such a short time? I assume that they were worried about benchmark results with some upcoming competitors (MS or Google), and they wanted to kick out a new iPad that would level those concerns.