Equipment: The trusty Samsung a920 music phone with Sprint PowerVision 3G service. No custom software, pure "stock" configuration out of the box.
Monday and Tuesday morning in New York City: Spot checks at various points both outside and inside plus cab-rides. Consistent performance with no drop outs. Didn't work in the subway.
Tuesday driving south on the New Jersey Turnpike via Edison, NJ to Wilmington, DE: In spite of dropouts around Newark airport (Sprints maps show no coverage holes there, btw), we had great performance south to Edison. Worked good during occasional checks during the rest of the drive. Perfect performance in Delaware.
Wednesday driving south on Interstate 95 from Wilmington, DE, through Baltimore, to the DC beltway: Near flawless with continuous listening the entire two hours. One re-buffer as I crossed the first bridge on the upper Chesapeake was countered by my amazement that it didn't drop out at all going through the tunnel in Baltimore! Breezed through the 90-degree route around the beltway and then out on the road to Dulles International Airport.
Conclusion: If satellite radio is the measure, then Internet radio via 3G is absolutely ready for prime time. My XM radio used to drop out when I went under dense pine trees and under some viaducts, even in area where there were ground repeaters (e.g. Palo Alto, CA on San Antonio Road heading towards 101). The continuous listening performance of Tuner2 radio on the Sprint PowerVision 3G network was just as good and the audio quality was much better. (Trust me - this is more than just a subjective statement on my part. Or better yet, don't trust me and take a listen for yourself.) Internet radio in the car is definitely a reality. Now we just need to let people know!