Hi Julianna!

Most of the low carb products are a YMMV (your mileage may very) kind of thing. Some people seem to be able to eat them several times a day and do just fine, others stall eating them only once in a while. Sugar alcohols and most artificial sweeteners seem to cause a problem for a great many people.
Fiber is a different matter altogether. Your body lacks the necessary enzymes to even digest it, so it passes out of your body undigested and does not contribute to either carb or calorie counts. I make my own version of the Flax-O-Meal with ground flaxmeal and wheat bran and have no problems with it. My DH loves the stuff and says it's the best thing for keeping him regular. I've never tried the granola. Never was too keen on granola anyway, so I can't see spending my money on something that wasn't all that great even at "regular" carb levels.
I do eat the Atkins pre-made bread and muffin mixes, but not every day. More like a couple of times a week at most. Often when I make a batch of muffins, I only wind up getting one or two because the rest of my family likes them too.
Generally, you're best sticking with natural, unprocessed foods as much as possible but everyone has to experiment and see for themselves how these things affect them. HTH