The effects of meditation are best compared to those of sleep. A good night's sleep doesn't make up for lousy sleeping habits the rest of the week. But getting enough sleep _regularly_ is key to being healthy, happy, and productive.
Ditto meditation. Trying it once in a while is likely as waste of time. But practicing it regularly (and getting better at it, which you will, with practice) can have positive effects, over time.
As an aside - Zen takes a good deal of commitment, but it's the least 'bullshity' of all the approaches to meditation/mindfulness I've encountered. Eight Gates of Zen is a great intro: http://www.mro.org/zmm/training/eightgates.php
In the Eastern religions this is very much what is referred to as "faith"; the study and analysis of meditation in this manner is intellectual, but meditation itself if very much anti-intellectual and seeks for the non attachment of intellectual concepts (a difficult concept to grasp for those of us raised in the rationalist philosophies of the West).
It doesn't mean that you can't measure it; it means that, aside from the sensations which come to you of well-being and effects that come to you from direct observation, you shouldn't be using it as your primary guide to the effectivity of meditation. Fortunately there's 3000 years of incredibly descriptive and academic Buddhist and Hinduist texts which talk about this in amazing depth, and have zero usefulness for your personal progress.
Right now, whatever comes up my mind i just let it be and think nothing of it. Null.
Oh, by the way, I also do self-hypnosis at the end of meditation.