Today, the Halifax published their price index for April. It showed that house prices are down over 5 percent from their peak of autumn last year.
I also compared the Halifax's seasonally adjusted data with the non adjusted counterpart. Since 2005, the seasonaly adjusted data has consistently understated the true level of price inflation. It missed the peak, but now also appears to be falling faster than non-seasonally adjusted prices.
Personally, I think seasonal adjustments are overused, particularly with data series like house prices. Recent data from the Halifax amply illustrate why we should be so skeptical of these kinds of adjustments.