I have an iPod Touch 16gb, using it for about a month now. I wouldn't want to own both devices, that would seem pointless. Although I think it would be great to have everything all it one, I think in its current form the iPhone isn't so good and I would stay with my Touch.
Reasons being, firstly, I mainly use my Touch on the train commuting into work, I always have music or video on it, so never feel that I have to be surfing the web, requiring the feature of the iPhone.
Otherwise its because:
- Slow phone data connection.
- Less storage.
- Using up battery life for the fact its a phone and media player.
- Poor camera.
- Can't use other brand headphones.
- MMS... forward messages etc...
I'd totally recommend the Touch (jailbroken), though it does have a few bugs. I say wait until they do something better with the iPhone.