Net carbs are ok! You are subtracting out the fiber, which can't be digested, and doesn't affect your blood sugar. Seems like cheating but it isn't! Look at it this way - if you counted all the fiber, then people would be less likely to get a high fiber diet, which is very important for everybody, regardless of plan! Fiber is essential, so don't feel guilty.
As for sugar alcohols, you don't need to count them either, but take it easy on them, they are a popular reason for stalling weight loss!