You have illustrated the benefits of actually holding the camera before you buy it perfectly. It can be the highest spec. camera in the world, but if it is not the right one for you then it is no good.

I think the Oly E510 has a few more benefits than just some extra pixels over the E500. But I'll leave that to the Oly users - I've got Canon .

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html