I dislike "Mindfulness in Plain English". I have not spent more than a few hours trying any specific technique it advocates, so it's really the writing and reasoning I recommend against.

I reviewed the author's claims in some depth a couple years ago:

http://jonathan.graehl.org/vipassana-meditation-part-1

http://jonathan.graehl.org/vipassana-meditation-part-2

http://jonathan.graehl.org/vipassana-meditation-part-3

I think, before adopting a regimen, we ought to ask ourselves: is there evidence that the advocates of it arrived at it by a reasonable process? Or, if they didn't, are the benefits (compared to alternatives) compelling enough to override the risk of your spending time making an assessment and making an error in the direction of credulity? (see http://lesswrong.com/lw/19m/privileging_the_hypothesis/ )