I'd highly recommend reading Dr. Raymond Soneira's outstanding article on the iPad 3. It explains a lot of the power consumption/battery issues.
The iPad 3 uses amorphous silicon which is not as power efficient as the IGZO technology on the iPhone. To quote the article...
The iPad 2 uses amorphous Silicon for the LCD Active Matrix Thin Film Transistors (AM TFTs), the same display technology found in most Tablets, laptops, and desktop monitors. On the other hand, the iPhone 4 uses Low Temperature Poly Silicon (LTPS) because the much higher ppi requires smaller AM TFTs in order to maintain satisfactory brightness and efficiency. However, it’s more complex and costly to produce. One of the biggest rumors was that Apple was going to use Sharp’s IGZO (Indium Gallium Zinc Oxide), which is better at high ppi and lower cost than LTPS. But it’s a new technology and Sharp publicly announced in December that it was experiencing startup delays. LG and Samsung have also been working on IGZO technology. The question is when, not if, this technology will be coming to future Retina Displays (and non-Apple Tablets and Smartphones). It will also be coming to laptops, monitors, and televisions, possibly even Apple’s. Our lab measurements show that IGZO is desperately needed for the new iPad high ppi display because of the high power and large batteries it currently needs. And, counter to the rumor mill, IGZO can do IPS (in Plane Switching) technology that is found on the iPad 2 and iPhone 4 displays. So what display technology is in the new iPad? According to DisplaySearch it is still amorphous Silicon that has been pushed to its extreme upper ppi limit.
Regarding the battery, when the iPad 3 battery indicator reaches 100%, in fact the iPad 3 has only charged to 90%. This is by design as the charging of the battery is not linear and charges very slowly from 90% to 100%. Again, from the article...
Conclusion – the battery is only 90% charged when it says 100%
So, when the battery indicator first says 100% the battery is actually only 90% charged and you get 1.2 hours less running time. It takes an additional 1 to 2 hours to fully charge the battery as explained above. However, anyone that recharges their iPad unattended (and off or in sleep mode), especially overnight, will get the necessary extra charging time and get the full running time indicated above.
Apple has subsequently released a statement saying that this is by design and as they intended. Maybe so, but why? ALL of our results are technically correct EXACTLY as stated above. So what’s the REAL reason – it isn’t the one mentioned in Apple’s statement. The battery charging rate gets slower and slower as it approaches full charge, so Apple decided to show 100% sooner so that people didn’t notice or get annoyed by the long and slow final creep up to the true 100% charge level. The last hour in the long 6½ charging cycle is painfully slow, so that becomes invisible if the battery indicator is accelerated up to 100% for that final hour. It’s all done to improve the quality of the user experience...
The full article can be found here.
http://www.displaymate.com/iPad_ShootOut_1.htm
It's fairly and objectively written, not out to bash the iPad 3. Other than the two issues, it recommends the iPad 3 as an outstanding piece of technology and praises Apple for pushing the technology forward.