I can't see such a boycott succeeding... too few people here want to do more than grumble occasionally. Americans have gotten "good" over the years at ceding real choice for immediate convenience.

But there is great GSM coverage, anyway. Spotty depending on carrier and locale, but great overall. I drove from north Texas to southern California a few years ago and only lost signal (AT&T) for a few minutes in the west Texas mountains. Other than that it was crystal clear and consistent.