I have a 2002 Prius, also. Have been running Michelin HydoEdges for about 25,000 miles. Had to go up one size to meet load requirements, but this did not affect speedometer reading. (Make sure you get tires rated for 44 psi.)
After 25,000 miles, you can tell that these are not new, but there is hardly any wear on them. I expect them to run 60 to 80,000 miles. (I am running 44/40.)
Had a rare rain storm in Phoenix last week, and almost plowed into cars stopping in freeway construction zone. Antilock brakes and HydroEdges saved me. Although, they didn't stop on a dime, I was able to stop noticeably faster than others and avoided being part of a pile-up. Had to watch rear-view mirror, though.
Check out Costco (special order), Discount Tire and Tire Rack (on-line). I think Michelin has a "buy 4 and get $60 back" special on now, though I am unsure of exact time period and amount. I got $50 back on my set last year.
The HydroEdges are worth the extra money and peace of mind...