Glad you dug it, thenewgreen, and thanks for the post, vile.
In my experience, guided meditations (whether app or audio file or live) can really go one way or another. Some create that extra layer ooli is talking about, making it even harder to escape the thought-snarl, and some surgically detach you from it. Not sure, but probably that style which functions best for one depends upon one. Sam Harris's deployment is some of the most effective I've experienced, personally.
It makes good sense to me, though, that guided meditation COULD work wonders for the one meditating, whether beginner or experienced. As near as I can science my way through this, when it works, it works by engaging the language centers of the brain. These same language centers might otherwise be spooling out an endless torrent of thought, drama, narrative, analysis, and all the rest of that which obscures the bliss of being in the present moment. The guided meditation, if executed deftly, occupies these centers without arousing criticism or accelerating the thought stream. In this sense, in my opinion, it performs the same primary function of the mantra, which drives other words off the tongue/mind by occupying that space, and thereby prevents more complex thought-forms from building in the mindspace. It's much the same principle by which drishti organizes vision and focus in yoga.
Anyhow, that's how it all shakes out for me. I frequently meditate in silence, but as silence is so hard to come by, and also for their many wonderful properties, I frequently meditate to the accompaniment of the singing bowls -- and if the mantra/guide feels absent, toning works well too. Here's a few tracks I have really benefited from:
This guy does some great composite crystal singing bowl tracks:
Emile de Leon gives you 70 minutes, all 7 chakras!
Don't really know if others share these leaps I've offered, but I owe my extrapolations to a great segment on Radiolab concerning language and bliss, and numerous conversations with my behaviorist colleague. Happy transcending.