Hey Sam, I can only speak for myself, but as many people here have stated, there are millions of teachers, gurus, systems, techniques, and styles all dedicated to achieving enlightenment, waking up, or finding inner peace. This issue is the same in Buddhism as it is in the fitness world. For instance, if you suddenly decided that you wanted to get in shape, what do you do? Crossfit, weightlifting, running, biking, swimming, martial arts, P90X, yoga, or should you train "instinctively" and figure it out yourself? The choices are overwhelming. As overwhelming as when picking a religion or meditation style.
For many people here at treeleaf, this Shikantaza is not their first taste of "exercising." Many of us practiced in other "styles" before coming here and when we found this we knew it fit for us. To continue my analogy, it is as if we were lifting weights, then went for a run and said to ourselves, man I've really been missing out on this running stuff. However, even if this is your "first" system I would recommend giving it a full and serious tryout because, here is the crux of the issue; there is nothing wrong with being a runner or weight lifter and there is also nothing wrong with a runner occasionally lifting weights or a weight lifter occasionally running. The issue at hand is that if you continually chase the next big thing, the next new system, you will never get fit and you will never get "better" at anything. I have seen thousands of weak and out of shape kids who have jumped from system to system, spending money and time chasing the next "easy way" when if they would have just stuck to a boring program in the beginning, they would have seen real results.
The same thing holds true for this practice as well. If we at treeleaf ran off chasing every idea that every new user presented, we would never get anywhere. So, as much as I like looking at youtube videos and reading new ideas, in the end I will end up "just sitting" and I will continue to "just sit" until I have sapped everything out of it (if that is possible) before moving on. That's not to say that I won't occasionally twirl around a mala for stress relief while driving, but my main effort is at zazen. And for some reason, if there ever comes a time when I need to set out on my own, I will have a strong base of shikantaza to work from.
I know my fitness analogy isn't for everyone, but I can't resist using it because I see so many similarities between people searching for spiritual enlightenment and physical enlightenment. I've watched many people endlessly worry about systems, plans, infomercials, and magical techniques, when if they had just done some hard work with a simple basic plan they would have been fit and happy already. So, I don't know much about Adyashanti's "true meditation" just like I don't know much about that "P90X" system on TV. They might both be the best thing ever. But I wouldn't know because I have a run to do and some shikantaza to knock out.