My Take
Provides the teacher with a tool to be able to create many different types of activities for the students to use. Some of these activities are very engaging towards the kids... i.e. Rags to Riches activity. Activities are easy to create, though for the most part are teacher created, not student created.
With quizzes and even activities, results can be recorded within a gradebook for review. One of the difficulties that I found with the gradebook was sorting through all of the information and knowing which quiz is each.
How I Use It
What I used it primarily for was for the students to take different quizzes. A number of different assessments were set up across language arts area primarily. Our spelling was done with quia where students needed to choose words that were spelled incorrectly.
It has been somewhat bandwidth intensive and could be slow at times, though it could have been more with our network. It's a great resource for students to be able to continue to interact in multiple ways with the material through teacher created activities.