I use L=awstats]http://awstats.sourceforge.net/[/L] it is a detailed setup, highly customizable log analyzer. If you have your webhelp on a server and are comfortable setting up a perl program, it is a great tool. If you decide to use it I have several links that are helpful with setup and I'm willing to help in any way I can.
Since I've installed it, it's been great to see that are customers DO look at the help—and often. We have about 100 banks we provide software to and last month we had nearly 1000 visits to our help and 250 unique users (internal and external).
Let me know if I can help.
Another more belt and braces approach would be to use the RoboHelp Server application. This gives you the ability not only the see the hits that your help pages get but also record the questions users ask for in the search but don't get any response. These and other reports are a really useful way to plug any documentation gaps as well as just recording hits.
The latest version RH Server 8 is a big improvement on earlier versions and you can publish to it from either RH7 (with the 7.0.3 patch installed) as well as RH8. I have a number of posts on my blog if you require further information relating to RH Server. Just select the "RoboHelp Server" category.