i dunno...
the iphone has a pretty sharp edge... we're going to need a comparison test for this :-)
Now look... In all honesty, yes backgrounding is nice. And while I would like certain things to background, it's really not all that important in the end.
I would rather do one thing extremely well as opposed to multiple things half assed. One of my biggest gripes with the windows mobile devices was that when you X out of anything, it didn't actually close the application. It minimized it.
Unfortunately no one told you this, and conventional wisdom of people who had been using Windows for years said that "X" means close, not minimize...
The only way to actually close the app was to open up the task manager and free up memory. which meant you had to open up another application and if you had too many things opened then you would have to reboot anyways cause the thing moved so damn slow.
It wasn't until i started hanging out at

A Developers and loading up custom ROMS that allowed things like "X" means close. Before that you had to "pay" to actually have a program that would close your apps...
So in my experience and understanding, Apple probably saw this as ruining the experience. They probably figured that it would be better to just say "when you push the one button on the screen, close the application entirely instead of having people forget what they have running and bogging down the system and eventually having to reboot... Like you would in a Windows Mobile Device."
They had to make a decision at the time, and I believe at the time it was the right one...
Of course now that Apple set the standard regarding mobile phones, everyone wants to copy what Apple did. Blackberry with the Bold and Palm with the Pre. However they said, "well let's just do the things that Apple couldn't or wouldn't do in the first place".
Not everyone who picks up an iPhone is as intelligent as we are to understand that running multiple apps on a device that has very little memory is ultimately going to crash it.
And remember... First and foremost... it is a PHONE. Not an iPod... So I think also that Apple chose to focus more on a communications device first, and a gameboy/drum machine/zen garden/fart maker/twitter device second.
Either way, give it time, and there will be things that people will be complaining about with the Pre too, and suddenly the iPhones will look like the saviour. Or maybe Nokia will come back into fasion, or perhaps Motorolla they haven't been doing much lately...