I used play support alot and it is my favorite role in league.
but there is that obvious evil ''wisper'' that you get while playing it.
basically as support you desperately need to play 100/100 to carry your team, not just 90/100... no really 100/100 the whole thing
why because you are not fiora that gets fed after 2 kills or fizz that goes beserk etc.
you are a playmaker that relies many times on others to follow up.
lets assume you are soraka and you heal your whole team all day 24/7, now it would be useful if your team actually fires at the enemy or engages instead of eating all the poke and delivering no damage, this could continue all day.
or you are alistar or sona and happen to pull off a Amazing game winning combo ''stuns'' etc and you even ping... now this requires a follow up and sometimes your team could be as near as 1 inch and not engage at all.
but what i consider the worst thing about support, is when you do happen to make that game winning pull/stun/engage/heal and you win a teamfight... your team is full health and decides to back without taking towers or baron.. you as support just stand there like some afker wondering like wtf can i do now.. because as any other role, you could easily solo a tower, but as a support you just look at the tower and do a maniacal laugh or cry desperately why why didn't anyone come.
aside from the abuse you can expect sometimes in lane from your adc master or jungler thats about sums up the problems in my games.
mind you there are many nice teams, more often then not the real problem is that NOBODY takes towers or objectives, you can keep making plays and they just teleport back.
despite that im still playing support and it can be a carry for the whole team, but more often then not it depends on too many factors.