the rumor about alltel being bought turned out to be true, but they werent bought out by verizon, they were bought by Goldman Sachs Group and TPG (Texas Pacific Group) Capital:
http://news.yahoo.com/s/cmp/20070522/tc_cmp/199700440
if you are after nationwide coverage, we at evdoinfo feel the best choice is sprint because of their roaming agreements. in addition to sprint native coverage, they have a roaming agreement at EVDO speeds with alltel, and roaming agreement with verizon at nat'l access/1xrtt speeds. the combination of coverage and roaming, gives sprint the largest 'footprint', in our opinion.
you might want to take a look at
http://evdomaps.com
its not a 'coverage map' per se... its a voluntary effort by members of evdoforums who are posting actual speedtest results and info about their gear, from many places they are in the nation.
everyone using evdo from sprint or verizon is encouraged to join evdoforums and plot your speedtest results.