For example, mixing: Woopra, Google Analytics, and Clicky. They all offer free services, and this way I could have more information.Are there any problems with this (e.g., slowing down the website, conflicts between the tools, etc...)?
Is it beneficial to use more than one website analytics application for a single website?
analytics
Google Analytics is very comprehensive, and widely used by most professional webmasters and SEM, which is why you'll see more questions about it here than any other analytics application. Woopra by the way is definitely not free: Woopra pricing, and either is Clickity: Clickity Pricing, so you'd be increasing costs by adding these (significantly for a large number of daily views).There's very little that you can't do or track using Google Analytics, and Google is continually improving it too. For example, they recently released Universal Analytics.As John points out, there is a performance cost with each set of tracking code and JavaScript file(s) visitors would need to download and run in their browser, making your site that much slower for both user and search engines (potentially impacting SEO), and increasing the load on your server. As far as conflicts, you'd likely see references to each in your results. So in short, I'd suggest at least sticking to the application that suits your needs (and budget) best.