My immediate impression from doing a half dozen searches at various times today is that it's fast! Much faster than, say, Technorati. Every search I did with Google Blog Search, the results were there in less than one second.
With my searches, it consistently turned up results that weren't in other search tools. Does that mean it's more accurate? Well, Technorati and Feedster both turned up some results that Google Blog Search didn't. So I'm as confused as I was before on how good any of these tools are.
I've resisted reading any detailed reviews or commentaries yet until I've taken a good look myself. But I am paying attention to Steve Rubel's experiment.