Not sure the best way to vote, there should be a "waiting for 30+ GB iPhone instead."
I could vote "8GB is enough for me" because it is as I currently use the phone. That is, I hardly ever use the iPod fuctionality. My iPod usage is as follows: my 5G Video iPod used in the car on my long commute, my Shuffle at the gym, my iPhone is my phone with little to know iPod use when I'm actually at work at my desk.
Now, if they were to come out with a 30GB+ iPhone I could fit my entire music collection on that and be able to replace my in car 5G iPod setup completely with the iPhone and be able to completely get rid of my 5G. In that sense, the minute the iPhone hits 30GB or more I'll be getting one and it will even let me get rid of yet another device.