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: 
**SHORT ANSWER**: 

You are correct to question the results; log analysis is not adequate to report actual traffic.

**LONGER ANSWER**:

WebTrends is a great tool for what it delivers. But as a previous administrator of a WebTrends installation, I found that web logs are notoriously bad at capturing metrics of interest.

For instance, if there exists any caching in your web delivery stack (or on the consumers side-- \*I'm shaking my fist at **YOU, AOL**!), then your web logs are instantly non-reflective of your site's actual activity. This is because log analysis assumes that all user consumption will translate to an HTTP request back to the web server-- and thus having been recorded in the IIS logs. In the case of a cache, this would not be the case.

In the future if you want more reliable results, you ultimately need to ensure that there exists a way to bust any caching strategy. The obvious answer is dynamic content. But if you do not want to rewrite all of your content in such a fashion, just ensure your web traffic analysis uses a dynamic call.

WebTrends actually offers a solution to this problem, called SDC server. This is exactly what Google Analytics offers as well-- it's a javascript call back to the analysis server.

...I could go for days on this. If you want more specific information, comment back. ;)

***EDIT***: With WebTrends, specifically, it is quite important to configure session tracking beyond their default IP/userAgent configuration. If your web server assigns a session cookie, you will find this will increase your reliability; especially for differentiating between users which may sit behind the same NAT.
There is a logging package for free from MSFT for viewing this information using SQL Reporting Services. Google it.