Cingular Wireless led in FCC complaints per 100,000 customers according to recently released data published today [paid subscription req.] in the Wall Street Journal. It has been nearly a year since we have published complaint data.
Complaints to the FCC against each national carrier per 100,000 customers
Verizon Wireless was able to keep the least complained about crown with less than one third the complaints of Cingular. It's not known if the data is new enough to include T-Mobile USA's recent Sidekick trouble.