To Smeargle, or not to Smeargle? That is my question.
While Smeargle is...very "versatile" by movepool, it has little viability in its versatility, especially for UU. Any fairly experienced player will know that you either A) are planning to do a BP chain or B) are aiming to troll via some level 1 set or C) setting up all them hazards.
Smeargle isn't very hard to take down. a BP chain is stopped cold via phazing (unless you plan to run Ingrain,) or via Taunt, one of which every team most likely carries. Any troll set can be taunted or KOed by multi-hit moves (which aren't that rare- Rhyperior Rock Blast, Weavile/Ambipom Beat up, Cinccino's TailSlap/RockBlast/BulletSeed). Hazards can be spun away or once again, Taunt. (see a trend? Taunt stops 99.999% of Smeargles cold.)
However, if it does set up, it's very dangerous. The ability to BatonPass anything (Shell Smash, anyone?) is incredible. The ability to set up all hazards is pretty nifty too. And admittedly, troll sets can often find a way to annoy the opponent.
But, in my personal opinion, I would say not to use Smeargle. It's only use is for more gimmicky playstyles, and there are often other, more viable options, like Mew for baton passing, a plethora of hazards setters with usable stats, and we have Sableye to troll the opponent already.
However, no one's stopping you from using it if you want to.
(Hopefully this helped!)
PS: While Competitive battling is very serious, there are gimmick sets, troll sets, and the like. We're serious, but it's not like there aren't any fun sets.
PSS: BTW, welcome to smogon! ;3