Software assisted differentiation

Is there anyone out there with experience using software to help differentiate instruction for students in math?

A couple of programs I've looked into: Aleks and Agile Mind.

I am interested in seeing if I can use something like this to help support my Numeracy students. Of course the websites are filled with anecdotal success stories and even data to support their claims of success. Has anyone reading this tried to use something like this? I'd really like to hear your experiences if you have.

Update:
Brainslug asks a clarifying question in the comments, and the answer is long, so I'm posting it here...

Short answer:
"differentiating" is edu-babble for providing different students with different instruction and/or assessment, as opposed to teaching the same thing/same way to all students in the class. Software might help with this greatly in my Numeracy class.

Long answer:
We have all of our students who test below 7th grade take our Numeracy class concurrently with Algebra 1. The problem is that skills range from around 2nd to 7th grade levels. Some kids need to work on place value and subtraction, while others are ready to tackle fractions. We decided not to split the class up into two or more levels to avoid the pitfalls of tracking in a small school.

So, to help students most efficiently, they need to be provided with instruction where they are ready to learn. One solution can be to split kids into flexible groups within the class, where the different groups are working on different skills. However, aside from this being an exorbitant amount of planning time, our freshmen generally do not have the student skills needed to work independently for long periods of time, or the ability to learn from static worksheets without direct instruction and good coaching.

The software that I mentioned above assesses students' "knowledge space" and then only lets them work on the skills they are ready for. The software provides explanations, examples, feedback, and so on. It also allows you to easily provide individualized homework and assessments. In my ideal scenario, I'd set up the class as follows:

Each week (or so), a new skill in math is taught. At the beginning of the week, all students take a quick diagnostic. If they pass, they don't participate in the lesson: they use the time to instead work on the software, on whatever skills they are currently building - plus, maybe some other problem solving curriculum. If they don't pass, they spend half the class (which is an 80 minute block) working with me on the lesson as normal: direct instruction of conceptual and procedural understanding, manipulatives when appropriate, and pair/individual practice. They would then spend the second half of the class working on their individual objectives via the software.

If this works, it would allow class time to be much more efficient, as students would only ever be working on material that was needed, and at the appropriate level. Of course, this all hinges on the software being able to make good on its promises. I'm hoping that the software is both understandable enough and engaging enough that my students can actually learn from it. Computer based learning could be just like a glowing worksheet, or it could make good use of video, animation, interactive demonstrations, and so forth to really move students forward. So my question: has anyone tried this with students?