“We have recently invested in a high end stats package that does a lot more than others we researched, and unlike what I’ve seen with Google Analytics, you can bank on the data you get. In using Google Analytics I’ve found that it only counts traffic from a slice of the actual number of visitors to my site. Some people speculate that it’s because Google’s third party cookie doesn’t get set on many people’s browsers.”
“Google Analytics registered half of the users we had registered through WebTrends, which was a little depressing.”
“Web traffic comes in hits …. each request from the browser to the server is a unique item, and there is no such thing as a session or a visit. When it comes to extrapolating derived metrics like visits, each web reporting tool uses its own algorithms to decide which group of hits belong to the same visitor, and which don’t, and you’ll get very different answers from different tools. A variety of techniques are used to identify which visitor is which (IP address, time, user agent headers, cookies, etc.) and none are perfect.
Hence, if you are using the web reports to make business decisions, it is essential to compare like with like.” (a guy from Convio)