I'm at work and trying to recall the name of the one I used to use for Marcel - I believe it was Michaels Probiotic - and it was from a really good health food store here in Phoenix - it was kept refrigerated (as many need to be). They had a ton to choose from, but I liked this one the best.
I bought this one *before* I had made contact w/ Susan Davis - if I had waited, I probably would have purchased hers as well as it has guaranteed potency and the FOS. (her probio doesn't have enzymes does it, Crystal?)
This is a great site for learning about strains:
Probiotics & Prebiotics - Acidophilus, Bifidobacteria, Align, Culturelle, VSL#3
You can see that Align is very good for IBS (and others). Here are some more that are generally considered better quality:
The Environmental Illness Resource - Treatment - Nutritional Supplements - Probiotics & Prebiotics