There are a number of different paid and free tools available to track web traffic and web related trends. I have used a number of them and many of them have their strengths and weaknesses. The choice/s of your selected web analytics software depends on the purpose of your website and how these tools help you optimize the visitors' experience on your sites.
For a small website, perhaps Google Analytics or Yahoo Analytics is best. What have been your experience using such tools? I have also used fee based web analytics tools like WebTrends and Urchin.

So the most important question is, what do you do with the web traffic data? Do you read the reports consistently or once in a quarter?

I am using google for long time.

Would you ever contemplate switching or looking into paid solutions?

I use a combination of Google, web stats from my hosting company, and a tracking software I purchased. I don't think paid solutions would be an option at this point, if anything I would look to pull the process more internal with tools I can purchase.

If you use a combination of tools it will avoid chances for missing cache.

There will also be differences in numbers between various web traffic tools because it depends if the data is from server logs or javascript.