Thomas Lang teaches the best method of foot technique, and his reasoning is perfectly valid. The idea is to not hang yourself on one thing, and play using whatever is dynamic at the time. For example, let's say you're playing such a song where the chorus bass drum work is much faster - obviously it's dynamic to play chorus parts heel-up.
It's difficult to get used to, but after forcing myself to switch between heel up and heel down in the same songs, I've noticed I have much more kick drum stamina, and I can incorporate accents in my playing using bass drum patterns. So it really is worth practicing whatever music you may play, and I'm actually pretty old school on foot method. I don't play with my foot down the center of the footboard - it doesn't feel right. The only difference between my heel-down and heel-up is my heel being raised slightly off the plate. I do use slide technique a lot in my playing, but because I've practiced it so much and used it over the years, it isn't really 'slide' anymore. It's more like a twitch.