Robin,
I have owned a Blackberry 7250 and 7100i. I do not have an iPhone yet. But plan to purchase one on July 11th when the 3G is released. In my opinion the BB is the king when it comes to push email and calendering. That's why I held of buying an iPhone when it was first released because it did not do this for corporate environments (Exchange Server).
With the new release of the firmware version 2.0, Apple has remedied that. From the demos I have seen it will work pretty much like the push email and calendering available on the windows mobile platform which work very well.
The reason I'm so excited for the iPhone is not because it does video and music (which is very cool). But because it has a full browser and you can have a slew of different applications on it. It really is a little computer with full web browsing in your pocket.
Will you be able to watch live TV over the internet? I don't think that is an option at this time. But you can download via iTunes a wealth of tv shows and movies and load them up on the iPhone.
For me Blackberry to iPhone is like Windows 3.1 to Windows 95. The advancement was revolutionary. Sure there are problems with the iPhone one that remains elusive and no one knows if it's fixed in the new firmware is that copy and paste do not exist. Also no Adobe Flash support.
Disclaimer: Sorry, at the time I couldn't think of a more revolutionary comparison than Windows 95.
Hermdog