I think the skin method for GA is the worst method to use.
Here's why:
1) you can't use a skin on more than one site : the skin is tied into the site. Many people use bought skins, and have to merge changes to get updates to those skins.
2) putting the code in the skin file means you track every single page on your DNN install, including admin and host pages.
3) you can't easily modify the code to take advantage of more advanced GA settings like timeouts, etc, without uploading a new skin.
4) you can't easily disable the tracking calls for testing/staging domains
A module based approach is much better. There are many around, including free ones. I develop and maintain a free analytics module, which you can get from http://www.ifinity.com.au/Products/Google_Analytics_Script_Module/
This module has the following benefits:
- only place on the pages you want tracked
- can exclude tracking for set security groups (ie admins). This stops your admin behaviour skewing statistics
- can modify the default timeout for the 'bounce' time
- tracks clicks to external links from your site (so you can see where your visitors are going after clicking a link)
- can exclude certain domain names (ie localhost) from tracking
- easily and quickly added to any site without skin modification
- inserts the tracking code at the end of the html page, per google guidelines
- can track registered users as an analytics segment
Given that analytics modules are freely available and have more features than skin based or 'head' based tracking, I think that every DNN site using Analytics should use one.