You cannot really compare ram usage from one machine to that of another machine. The performance of 512MB of ram on the iPad 2 could be equal to that of 1GB of ram on the other tablets. We just don't know.
The only other thing I can tell you is that by talking about it on this forum isn't going to make it magically happen. At this point if the iPad 2 is coming out in a few months the product is already finished and is being manufactured as we speak. Sure we could sit here all day and wish and hope but the fact is that it is too late. The specs are locked in. In fact they may have been locked in already for 6 or 12 months. Apple doesn't just wake up one day and decide to change something. It takes many months of planning and logistics to get things put in motion to manufacture that many products of this caliber.
Personally I'm not thinking about the RAM in a "how the machine runs" kind of way.
The Amiga 1000 in 1985 came with 256MB of memory
The Amiga 500 which came out a little later had 512MB but had a small trap door underneath where a 512MB memory upgrade could be fitted in.
I bought this extra memory upgrade at the same time I bought my Amiga 500, simply because some games needed the extra memory to run.
The "Devs" at the time could do more advanced programs if they had the extra memory space to work with.
It had nothing to do with The Amiga's desktop working any better, it just gave the devs more space to develop better software.
That's my same reasoning being the iPad's RAM. No I don't thin 1GB as the other tablets will have is needed to Safari or the photo app, however it would allow developers to write, or port over some more advanced software that otherwise they could not do.
No one in their right mind should ever want less RAM, that's just moronic and holding back some software from being created for the platform.