I recall reading a post some time ago in which Cathe said Low Max is really not true interval training. In the Low Max description, it's considered a "high intensity, low impact" workout. Effective interval training will have the high impact.
I also try to work in one day of interval training per week. The week I do Low Max I will usually do another workout (or two) that week that has some sort of interval blast in it as long as it's advanced (like SB) but it doesn't have to be an hour's worth (like the Imaxes). Low Max gets the heart pumping and the legs working hard. I have found that a week or two like that once a month doesn't take anything away from the results I strive for from interval training and actually helps. But that's what works for me!