Question: Any suggestions for an accurate Web Log analysis tool to generate reports on the IIS logs? We used WebTrends, but I don't feel it was accurate.

Answer: 
To analyze weblogs, I don't think you can go wrong with Analog: <http://www.analog.cx/>

If you are analyzing your own logs, which are often huge files, you will want the fastest analyzer you can find. Analog is fast.

You'll want one that's been around awhile and is still supported. Analog just celebrated its 10'th birthday. 

Analog claims to be the most popular logfile analyser in the world.

Multi-languages.

Did I say its free and open source? 

As far as accuracy goes, no tool gives perfect results. Javascript fails often in catching hits. Trying to track individual people's paths through a website (i.e. for Analytics purposes) is fraught with problems. And even trying to differentiate hits versus visits and screening out the bots is all more of a black art than a science.

What is best is simply to have a tool that gives decent basic statistics that tell you what you need to know.

I've looked at other tools, such as Deep Log Analyzer: <http://www.deep-software.com/>, which attempts to do analytics from your weblogs. But speed was a problem. They claim their new version 3.5 - April 2008, which I didn't try, has improved performance. The big advantage of a program like this is the advanced reporting you can do, including custom SQL requests. You have to purchase their professional version ($200) to do most of the analytics and custom queries. If Analog is too simple for you, then try the free version of Deep Log Analyzer.

And you can also try Microsoft's own Log Parser, as was the recommended answer in: <https://stackoverflow.com/questions/157677/a-good-iis-log-viewer-for-large-log-files>.
But you will need some extra skills to use it.
doing it with the logs is only a good idea if it's internal - I'd use google analytics for anyhing on teh internets