I would say that Combofix should only be used as a last-resort, when everything else fails and for some reason you don't want to start with a new load/image.
This. ComboFix is a hugely powerful program that has a ton of features. However, I would really advise that the average Joe really shouldn't use this as their go-to program every-time they think they have an issue with their machines. It is a very powerful program but could end up doing more harm than good if used unwisely.