This has nothing to do with iphones, but.....
I know nothing about the Mythbusters and there exhaustive research on this, but generally you are right, and there are rarely issues. The problem is that certain cell frequencies and certain ILS freq's, and possibly certain harmonics of those freq's, that under rare conditions can cause some distortion. It does not happen often or regularly, but imagine the next time you are landing in minimum weather the possible degradation of the signal that a phone may be causing.
We had a situation that we suspected possible cell interference which resulted in a few go-arounds to a certain runway at a certain airport. I don't believe it was ever able to be eliminated as the cause.
Hopefully some day it can be proven that it causes no problems, or those theoretical risks can be sufficiently mitigated, but the rules are there for a reason.
And yes, you can use your Ipod as soon as the FA's start talking after takeoff until 10 minutes prior to landing when they are securing the cabin.
And just to keep it iphone related, I am looking forward to getting mine in a few weeks.
