I really just do not understand the anger people are showing towards those questioning the memory on the iPad2. When it comes to iOS and it's advances to date, the limiting factor for "old" hardware is the amount of memory. The iPod Touch 2nd gen and iPhone 3 are capable of handling what iOS 4.2 and below can offer, EXCEPT for the memory requirements.
No is asking for a something that will last 5 years, and be able to handle every new feature coming out. But it is reasonable to ask for hardware that can run the new iOS for the two years after purchase, without feeling like you are watching a spinning beach ball constantly.
Yes iOS appears to be a lot more efficient with the RAM it is provided. But as others have already pointed out, the present version of iOS takes up at around 150M in memory just to boot up and sit there doing nothing. That number isn't going to decrease over time. So expect the iPad 1 to have worse and woerse performance over time, just performing the same basic tasks(when you update iOS).
Sometime in the not too distant future, iPad2 will be left behind by an iOS update. With 1Gig in RAM instead of 512/256, it would have been able to make that jump. And the performance of the iPad2 will have already greatly decreased, due to increasing memory demands, prior to that.
Apple users have always enjoyed something PC fans could not - having their hardware last a long time and continue to be productive all that time. With the presumably underspec'd RAM, that is no longer the case with the iPad line. You got two years of tip quality use, some didn't evn make it a year with iPad1 apparently, and then you are on the treadmill the PC side has always been on.