For a while during the summer I got C (I'm usually D) for about a month, due, mostly, to it being a somewhat stressful period in my personal life. During this time my bloating became really bad - as in, all the time, and painful. I had some of Heather's fennel tea in my cupboard - I usually just use it whenever I get really bloated, i.e. after the fact - and it does help. But I found it to be a godsend for actually preventing bloating and helping to get me stabilized again. For me, when I was C, I found that I really needed to drink 3 cups of it (brewed really strong) throughout the day (1 in the morning, 1 after lunch and 1 after dinner), every day, to bring down and then prevent the bloat and pain. It really really helped, but I really did need to completely overload on it - as in I really needed all 3 cups. I've kind of backed off on the fennel a little because I've gone back to being mostly stable (with occasional D) and don't find that I need it as much, but it sure did help me get through the workday during the summer!
Anyway, just wanted to share my experience to let you know that it CAN BE really helpful - but you may need to be drinking more of it to realize the benefits!