I liked them, and hated them. Being that TLK and SP were (partially) based off of Shakespeare plays, it would only make sense to have some comic relief. And of course, they were vital in TLK teaching Simba the meaning of Hakuna Matata. But sometimes I just downright hated it, when in the heat of a moment here comes Timon and Pumbaa with another pun or fart joke that just makes me cringe.
Not that jokes are bad, but they're always at the wrong time and it's like trying to laugh at a funeral. I always hate when Timon laughs at Simba whenever he explains about what his father told him stars were and how he says "What mook made that up?"
Anyway, good characters, but I still think they're a tad annoying at parts.