All yogurt has "yogurt cultures," which, I understand, help your digestive system. Their little yogurt civilization travels from its container into your gastrointestinal areas, where they set up shop helping you digest other foods and regulating the flow of foods into the intestines...or something like that.
Probiotics go one step further. They are helpful, microscopic little dudes that usually get added to the already helpful yogurt cultures, and they all work together to achieve gastrointestinal regularity. If the normal yogurt cultures are the army and navy, these little probiotic fellows are the marines. I don't think any microorganisms are sophisticated enough to have an air force yet.
Anyway, I'm not a biologist or a doctor, so please disregard the two previous paragraphs completely. Unless you're a doctor and you would like to correct my silly probiotic analogy, in which case, you may do so in the form of a comment below. I never took many biology or medical classes in school because I was far too squeamish. I would have fainted at the first discussion of blood-borne pathogens or communicable diseases. The hypochondriac in me would have immediately began drawing similarities between said diseases and the symptoms of my last cold, and it would have made me quite miserable and paranoid.
On the downside, Trader Joe's Organic Lowfat Yogurt Wildberry Probiotic Smoothies are not ultra-filling like the cream yogurts and the bottles are incredibly small. I could easily polish off all four drinks in one sitting. They are one or two gulps-worth a piece. Somehow my wife can draw out the consumption of these things for 20 minutes or so, but that's really not saying much. I once saw her - and I am not exaggerating at all - take two entire days to drink a single can of diet soda. She carried it with her sometimes, she'd put it in the fridge, then take it back out...then she'd have it on her desk. I must've asked her if she was done with the can like half a dozen times, and she would say "no." Apparently, she enjoys flat soda as much or more than fresh soda. But anyway, my point is that if you're a really, really slow drinker, you can nurse these probiotic smoothies for a few minutes max. They're very small and not very filling, and they're not dirt-cheap, either. We payed something like $3.79 for the 4-pack.
We also tried the strawberry version. It's good, too, but Sonia and I agree that Wildberry is ever so slightly better, though.
In review, TJ's yogurt smoothies are delicious and good-for-you, but there's not enough in the bottle. Sonia gives them a 4.5. I would have been tempted to give them a 5 if the serving size were bigger. 4 from me. Bottom line: 8.5 out of 10.