Local iPhone owners grousing about AT&T and pining for Verizon may want to check out the latest report from Root Metrics.

The Bellevue company charts real-world performance of the major 2G and 3G wireless networks, using "crowdsourced" data pulled from a network test application Root offers for mobile phones.

AT&T's service in the Seattle area -- where the company's wireless business originated -- fared well in Root's latest report, covering the period from February 2009 to October 2010.

It actually provided better coverage than Verizon, Sprint or T-Mobile USA, posting the best "RootScore" based on voice service, signal strength and data rates.

T-Mobile also fared well in the report, probably reflecting the Bellevue company's push over the past few years to upgrade its network. T-Mobile and AT&T both showed better-than-average data download and upload speeds.

The report is based on 450,408 samples on AT&T, 457,239 on T-Mobile, 453,189 on Sprint and 475,053 on Verizon. The samples were from apps running on BlackBerry and Android devices, plus some Windows Mobile samples in 2009.

Skeptical iPhone users may want to check out Root's new app. The company is releasing a version for the iPhone 4 that displays AT&T's signal strength and data transmission speed where they're standing. It also displays Root's network mapping service in real time.

For comparison, the app also displays how other major networks are performing at the user's current location.

Here are excerpts from Root's latest report showing average carrier performance:

Another excerpt, with more details for Seattle coverage: