Sharing mp3s is technically illegal.
As for downloading a file from a webpage, the iPhone wasn't really built like that. Accessing the file system without jailbreaking it is impossible.

To be honest, the iPhone isn't for advanced users. If I got an iPhone, I would still carry my n900 around. For the things it is meant to do, the iPhone does it very well.

The iPhone wasn't built with geeks in mind. It was built for people who just want to a phone that can entertain them on the side. The n900 was built to be a workhorse. While the n900 can do a lot of the things the iPhone does and even more, the iPhone is better at most things they have in common.

Look at web browsing for instance, on the n900 you get the full web at a cost: browser speed. On the iPhone, pages load faster because it isn't the full web. It is trade off. Apple won't add flash if it makes their device slow. Apple won't add flash when they know their browser can't handle it as well as a competitor's browser. I've noticed that apple only adds things when it can be better than re competitor. Look at the front acing camera. From what I saw at wwdc, the images were clearer than ours. Facetime is wifi only because apple knows putting it over 3g would expose a shortcoming. Now skype even wants to make use of facetime