Will Thalheimer of willatworklearning.com has $1,000 for the course designer who can prove that "an e-learning program that utilizes learning-style information outperform an e-learning program that doesn't utilize such information by 10% or more on a realistic test of learning, even it is allowed to cost up to twice as much to build?
$1,000 says it just doesn't happen in the real-world of instructional design. $1,000 says we ought to stop wasting millions trying to cater to this phantom curse."
I've never put much trust in designing to "learning styles" primarily because I don't agree with the theory, can't find the appropriate measurement tools and I question the cost of development. I think Will's money is safe.