GNC's Ultra Probiotic Complex is by far the most effective probiotic I have ever used. Your best bet for buying this is to catch it on the bogo + gold card which will run you $17 a month. It seems expensive, but you are getting 25 times the amount of CFU's as the cheap stuff at the grocery store.
I used probiotics because I had inflammation throughout my digestive track due to extended use of antibiotics and a trip to africa (long story) and after trying some of the lesser potent probiotics found at grocery stores and wal-mart I decided to go with a stronger complex. I used this product once a day right before meals with a glass full of aloe vera juice and I saw a significant reduction in my inflammation. In my opinion, if you are going to take a probiotic make sure it is at least 10 billion CFU's because you will not see much difference taking anything less. For healthy people who regularly exercise the jury is still out as to whether or not you will really benefit from taking probiotics, however, if you have any kind of digestive issues or would like to control IBS symptoms I would highly recommend this product.

Really great to keep your digestive tract in order as well as your immune system up. I Originally started taking this to be more regular(I hate not being able to poo). This product came out and I thought I would give it a shot. Within 2 weeks I was regular and I feel so great! Not only that, it is one pill a day and now bc I am where I want to be I only use one pill every 2-3 days.