My Take
ST Math, aka JiJi (the site's penguin mascot), is a great learning and practice tool for maths. The students are motivated by passing different levels and teachers can easily monitor student progress and activity from their own laptop/tablet/desktop.
Initial setup is a bit arduous as students have to learn their (very long) visual passwords, BUT I am always amazed at how quickly they remember because of the way students are "taught" their passwords - very cool.
Another great feature is that teachers can control and organize what is taught/practiced according to their standards/pacing calendars.
Overall this is a really effective tool for teaching concepts and majority of students really are improving their skills because of it. Our district piloted the program 3-4 years ago and it was so successful that it is now required.
How I Use It
Our school site has a computer lab and netbook carts. My class uses it for 50 min/week in comp lab, then 2x/wk on netbooks in class for 30 minutes.