I've been looking at the radarlogic data pretty closely for the last couple of months. It's nice that you can get daily updates, and apparently they are kicking case-shiller's butt on trading volume.
According to their data, Seattle "peaked" on 6/26/07 at $236.07/sq ft - and is off 7.5% from that per their latest quote ($218.38 as of 12/14/07). Based on the 28-day moving average that's an annualized rate of decline of just over 16%!!!
I can't seem to find futures quotes for Seattle.rpx index. That would be interesting data to have.