Good letter writers write letters

"Market letters tend to lag behind the market since they generally respond to demand for news about recent activity. Although there are certainly important exceptions, letter writing is often a beginning job in the industry, and as such may be handled by inexperienced traders or non-traders. Good traders trade. Good letter writers write letters."

So said Ed Seykota famously in his Market Wizards interview.

Once in a while, I get chance to read some analyst or broker reports, be it relating to specific stocks, commodities or sectors, or general market conditions. How useful are these to a trader? How much reliance can you put on them?