I used mods and cc a lot for TS2 and still do on my old XP computer, although admittedly not as much as I used to.
I don't use any for this game. I do use cheats, sometimes to fix game issues like mistaken vampires and sometimes to max stats so that I can actually do something productive with a particular sim but that is pretty much it. I don't even know what mods exist for TS4.
I would like more hairstyles but I am wary of overloading my game's memory on this PC so I am making do without. My game is plenty weird enough (two deaths on a date, toddler on the roof, etc) without mods :/