I posted a little over 8 months ago about a set of Bridgestone Ecopias that I completely, totally destroyed in less than 12,000 miles. Maybe 20% tread left at 11,800; properly inflated and aligned; all tires wearing the same. The tire shop was surprised but after checking the alignment they gave me a 60% credit on the warranty. I went with Michelin Harmony's on the recommendation of someone here and can say they are night and day better. 15,000 miles on them now and yes, there is some visible wear but it's not bad. I'll never use Bridgestone's again. Even the stock Yokahama's gave me 20,000 miles. I do commute down a windy road; here's a video of it; it's 4 miles long. Start at about a minute 20 seconds and watch it until a little before three minutes and you get the idea what the 4 miles is like.. This, combined with the car's weight and smaller wheel base may make certain makes of tire poor choices for me. I'd say the Michelin's are the only way to go in a Prius unless most of your driving is on flat terrain and in straight lines.
People that don't commute this road or ones like it don't seem to have the same problem with Bridgestones wearing out in less than 12,000 miles.