ive actually never really been frustrated by his shrooms. ive actually never played him up until yesterday since he was free and it was a pretty awful experience. the playstyle is just boring and his voice is probably the most annoying thing in the game, i always assumed he was a male, and his lore states that he is, but i believe he's a few tacos short of a fiesta
I only play dominion so I can only speak for Teemo there. I asked the same question once. You will see a Teemo in 85-90% of the games you play, most cases on both teams. His map control with shrooms is ridiculously good for Dom, and every one of his abilities make him the ultimate kiter. Shrooms to keep you at bay, oh you got a gap closer? Blind so you miss everything, drop another shroom to gain distance, speed boost is needed rinse and repeat. Couple that with flashes, exhaust, the little bastard is just straight annoying. If your team is too lazy to buy oracles, like most pugs are, then you will be at half health or less without adequate resistance gear before you even reach a node. His fairly simplistic play style and spells that overly benefit each other make him one annoying little shit. Again, I'm speaking from a Dominion perspective. I don't know how good or bad he is in Summoners Rift.