The G1 smartphone — due out next week — is poised to give Apple’s iPhone its first serious challenge.
For its part, the iPhone 3G has maintained strong growth, with a steady flow of mobile subscribers switching to AT&T for the iPhone in the two months since the device launched in mid-July, Nielsen Mobile reported Thursday.
Between June and July, the number of customers switching to AT&T for the iPhone increased by 97%.  Postpaid network adds for AT&T grew by 70% during the same period, according to Nielsen.
So far, the iPhone 3G has …