Sustained-release niacin is well known to cause hepatic toxicity. This is reported both in the label that you reference, and in the primary literature. These problems do not occur with immediate-release preparations - only with sustained release (such as Niaspan). So that is worth being aware of.
Statins are among the safest drugs ever used - so much so that most medical people talk about trying to give them to more, not fewer, people. Like niacin, statins can lead to insulin resistance. Statins don't appear to increase cancer risk, which was in question for awhile. There is some literature supporting the notion that reduced LDL may lead to increased cancer, but this is not dependent on the mechanism of cancer, and this conclusion is not yet supported by enough data to make it a concern for anyone. Heart disease is what will kill most Americans, so this is still the primary concern.
Statins are among the safest drugs ever used - so much so that most medical people talk about trying to give them to more, not fewer, people. Like niacin, statins can lead to insulin resistance. Statins don't appear to increase cancer risk, which was in question for awhile. There is some literature supporting the notion that reduced LDL may lead to increased cancer, but this is not dependent on the mechanism of cancer, and this conclusion is not yet supported by enough data to make it a concern for anyone. Heart disease is what will kill most Americans, so this is still the primary concern.