For the past year I've been using Data Archiving Services alongside the statistical logs provided by my host. While I have found the service useful, I've decied to drop it as it sometimes makes my website slow to load. Each time I get a hit, DAS is pinged with information about the visitor — this ping sometimes takes a few very noticeable seconds. The truth is, DAS really didn't offer anything beyond what I already had available to me. However, it does present the information that I care most about in a much more readable and 'pretty' way than http-analyze, the logging software provided with my hosting account. There are two things that I need when it comes to website statistics: 1.) the number of hits a day [week, month, etc] with the ability to have it not count hits to certain URIs (e.g., hits on my syndication feed) and 2.) referrer statistics — I like to know where my readers are coming from. Both of these are handled nicely in DAS and horribly in http-analyzer, not to mention that the latter's inferface is ugly and gives you no configuration options. The entire http-analyzer suite is quite powerful and offers statistics on a wide range of traffic data, but gives you absolutely no way to specify how you want this data presented or grouped — it makes me nuts.
That said, I don't have much choice but to use it as it is all my provider offers. Because of the wretched way in which it handles referrers, sometime in the near future I plan to add a "referrers" page to the site so that myself and others can see this information in a way that I find useful. I'll probably use either Dean Allen's Refer or Stephen Downes' Referrer System. Truth be told, I'd rather use Apache directly for this sort of thing, but I don't have access to httpd.conf on the server.