The research on Tabata intervals is actually pretty interesting: http://en.wikipedia.org/wiki/High-intensity_interval_trainin...
If you Google for "tabata research", you'll find a number of studies -- including the original paper by Dr Tabata [http://www.ncbi.nlm.nih.gov/pubmed/8897392] -- showing that bursts of very high intensity exercise can have a greater effect on endurance than long, steady workouts.
On the one hand, I find it counterintuitive (how can sprinting on-and-off for 5 minutes help my endurance more than running for an hour??). On the other hand, it kind of makes sense, since your body improves most when you really challenge it, and sprints are generally more challenging than a steady pace.