What are the benefits and risks of the use of statins?

The benefit of statins is massive, it lowers blood cholesterol, in particular the low density lipids associated with athersclerosis. This helps to prevent in turn coronary artery disease, and will very much decrease the chances of the person suffering a cardiovascular event such as a heart attack by 60%!.
Another benefit is its effects can be seen within a week of commencing the drug, and so is both of short term and a long term use for control of cholesterol levels.
Statins can also increase endothelial function, modulate inflammatory responses.
It also helps to stabilise atheromatous plaques so that even those with arteriosclerosis can use this with benefit, as it prevents the chances of this plaque causing further damage by rupturing and the creating a clot in the affected area. All of this results in less thrombus formation, which is effectively what causes many of the problems.
Even those without high cholesterol should be encouraged to take statins, as it also decreases the rate of cardiovascular problems in the healthy.
Statins are also suggested to decrease prostate cancer rates, with up to a 20% reduction in the population in those using the drug.
However, statins do not decrease triglyceride levels, and this will need to be done via other routes.
Most side-effects are not dangerous and only involve thing s such as muscle cramps, and pain in the muscles.
Renal failure has occasionally been recorded, but on a tiny scale, as is muscle wasting.
Statins should not be combined with fibrates, as this massively increases the risk of side-effects, and people should avoid grapefruit as this inhibits the action of statins.
Overall, the pro’s far out-weight the cons, in particular for those with high cholesterol who would most likely suffer if they did not take this drug.
There is more detail i can give if you want it, but i feel that is a fairly good summary