The short reason: The CPU has apparently not gotten a clock speed bump--supposedly containing the same dual-core 1GHz CPU as the iPad 2 paired with a new "quad core" GPU (which doesn't mean anything significant at all) and 1GB of RAM (instead of the iPad 2's 512MB), thereby changing the combined chip's moniker from the A5 to the A5X.
That short reason doesn't tell you the whole story, though. I don't actually care that the new iPad isn't quad core. I don't care how it compares to its competitors in terms of raw CPU power. As everyone who is concerned with actually using a device should be, I am concerned with the experience of actually using the device. Apple has done an excellent job of making its operating system run much better on its hardware than most competitors have managed. It doesn't need similarly powered hardware to drive the same level (or even a superior level) of performance in areas that drive the customer experience. The iPhone 4S contains a dual-core 800MHz processor but still manages to be the most responsive phone on the market--more so than the 1.2GHz dual-core CPU in the flagship Samsung Galaxy Nexus running Ice Cream Sandwich or the numerous higher-clocked CPUs in other Android phones.
So it's not a matter of thinking the new machine won't drive a great experience. I don't care that it's not at least certainly clock speed. I do, however, care that its CPU is the same as the iPad 2's. Having the same CPU means the new iPad will be able to provide a great experience for a smaller period of time after launch than the previous iPad could.
The simple thought process is this: The only things separating performance between the new iPad and the iPad 2 are amount of RAM and the more powerful GPU. According to Apple, the new GPU in its A5X processor is twice as powerful as the one included in the A5. This won't translate very much to better performance, but rather was a necessary jump in order to support the new display (which has 4x more pixels). The speed improvement will be negligible in apps that aren't graphically intensive while many developers of graphics instensive software will have to diminish effects used in software that previously ran smoothly on the iPad 2 if they want it to run at the new iPad's native resolution. In effect, the larger resolution makes a larger performance impact for graphics instensive applications than the gains offered by the new GPU. That means, at best, the GPU won't make this iPad feel faster but will make things prettier. The RAM increase will also likely be entirely compromised by running art assets for applications using the higher resolution.
In essence, the performance of this iPad in practice should be essentially indescernible from that of the iPad 2. I happen to think that, until the new iPad, the iPad 2 was the best tablet on the market for very nearly everyone. This iPad should feel essentially exactly the same, but with LTE for faster cell access (if you use that feature) and with remarkably prettier visuals. So that means it's the new best tablet on the market. Then what's the problem?
Simple. Contrary to what many people think, I don't always buy the newest and greatest things. I used my old iPhone 3G for nearly 3.5 years before finally updating to the 4S. I spent quite a bit of money building my PC for college, but used it until it was a husk of a machine. Ditto for the 5.5+ year old white MacBook I'm hoping to replace some time this year. I spend money to get what I want, but only if I'm confident it will be a long-lived purchase.
After the 2013 iPad comes out and new software takes advantage of its increased performance, software will start to feel slow on the 2012 iPad at roughly exactly the same time it begins to feel slow on the iPad 2. The new iPad will probably be supported with software updates for longer than its predecessor, but its "feels fast" timeline essentially has the same end-date as the iPad 2, with a year-later starting point. I'm having a very hard time talking myself into that.
So, for now, it looks like I'll just deal with my original iPad until next year. If something happens to change my mind, I'll probably update here. Certainly, though, if for some reason I have to buy a new tablet this year (right...), the new iPad is the one to buy. It is definitely worth the $100 premium over the iPad 2's price. It will feel the same but look significantly nicer. Anyone in the market for their first tablet can't really do better than the new iPad. The longevity issue also doesn't matter as criticism for anyone who purchases the newest model every year. Those users aren't going to be using this year's model for long after the next one is out and won't deal with software not optimized for it.
The thing is, I have an iPad. It's nowhere near as nice, and is already losing support on some of the software out there, but it's already paid for. I also have no compulsion to buy the newest model of any yearly gadgets. So I don't feel like putting down $829 for a new product that gives me effectively 1 year less value than if I had spent that money last year. (Besides, the new one still tops out at 64GB, which has been frustratingly limiting on my original model.)
So there you have it. I still think the new one is a great product, but for someone who already has one and doesn't need the latest and greatest, it's currently a pass.
Here's to next year, which I will almost certainly pull the trigger on.
Footnote: At the end of this year, though, I will have neither the newest iPad nor the newest iPhone. But hey! A new computer and Wii U can take up the slack.