My cat has FIV, heart murmur, kidney disease, and IBD. He was losing weight, had itchy skin, dirty ears, weepy eye, loose stool, and vomiting. He was on a hydrolyzed diet for years prior to this, thinking it was a food allergy, and this helped somewhat, but when he seemed more uncomfortable I knew I needed to keep searching for the problem. One expensive vet test (sent to A&M) showed a possible gut imbalance but did not have details on what was actually going on, and the only suggestion was use fortiflora which I had already been using (to try to improve appetite). My vet had not used fecal pills before so was fine with me trying them, but did not have any experience to share about them.
I submitted two samples to Animal Biome for testing, before and after using the Animal Biome products. The first showed my cat had an overabundance of bad bacteria (e coli) and very little diversity of good bacteria (2 types took up 80%). The consultation was very helpful in deciding what to try. After 30 pills of Gut Maintain (to try to get rid of the bad bacteria), and 90 pills of Gut Restore (as well as a diet change to single protein food, and budesonide recommended by my new vet) I retested. His results showed no bad bacteria, and an improvement in diversity of good bacteria. His gut is still considered imbalanced, and they recommend more sporadic use of Gut Restore to keep him on the right track, as well as their Mushroom Blend which I have not tried yet.
Because I changed several things at once (fecal pills, diet, and steroid use) it is hard to credit Animal Biome products alone, but regardless the test shows changes.
According to their own study, some cats will respond to Gut Restore and some won't, so for me, these test results help me decide if these products had any effect. I would recommend the test if you can afford it.