I took Threelac last year and found it significantly improved my symptoms. However I stopped taking it because I was allergic to the yeast.
Symbion is virtually a Threelac clone except it does not contain yeast. I've taken Symbion for the last couple of days and can report the exact same initial side effects (constipation, blotchy hands, white tongue) I experienced with Threelac, with the exception of the yeast allergy. Although it is far too early to say whether it will help me, it certainly gives me the 'feel' that it is very similar to Threelac.
I think the main bacteria that does all the good in Threelac is Bacillus subtilis. It is interesting that each sachet of Threelac has 500 million Bacillus subtilis, whereas Symbion has only 100 million. I only took one capsule of Symbion each day, but going by my very strong initial response, there is no way Symbion is only 20% as strong as Threelac. The Cobbs say two capsules of Symbion is equivalent to one sachet of Threelac. My early feeling is that this might be pretty accurate. I remember a sachet of Threelac hit me like a bag of bricks when I started it.
So, if you had problems with the yeast in Threelac, I would definitely consider trying Symbion. IMO, Bacillus subtilis just might be the most therapeutic probiotic strain out there. It stimulates the bowel's immune system, something those of us with intestinal candidiasis really need. It also helps heal leaky bowel.
I think proof of its powerful immune stimulation is that after only two days my tongue has gone particularly white. I take this as a sign of a strong GI immune response.
One piece of advice though. Don't be tempted to increase the dosage too quickly or you will look and feel like death warmed up. Best to start with a low dose and only increase by one capsule every 3 weeks. Be patient. It may take 2-3 months before you notice any improvement. I'm basing this advice on my experiences with Threelac.