It's good to be cautious when starting something new, but in this case you'll be good to go. Like Canyonbabe said, Digestive Advantage is simply a brand name for a particular blend of probiotics (many of which can be found in regular ol' yogurt); many people on this forum use this brand as well as other brands of probiotic blends. You might want to start off taking less than the recommended dose at first; some people experience an increase in gas in the first couple of days. It's kind of like if you start taking a fiber supplement all of a sudden, you might notice increased gas - but it will go away on its own in no time.
Good luck - probiotics have helped many people combat their symptoms of IBS (constipation and diarrhea alike) and hopefully it will work for you.
Does this product have any benefits for the IBS with predominant C patient? My experience with probiotics has not been terribly positive. Folks who favor IBS-D seem to respond better to many of the treatments currently available (anti-spasmodics, anti-depressants, etc) so I tend to shy away from many of these products.