Originally Posted by Jaysend
I had mostly positive experiences with my 980ti SLI. When it works it is fantastic. If it doesn't work, I run on one card.
This is the problem. Subjectively, the severity of the problem depends entirely on what games you play. For example, Gears 4 / Forza Horizon 3 / Path of Exile / Arkham Knight / Wolfenstein / Unreal Tournament are all games I spent a decent amount of time with which cannot use SLI - and the experience suffers significantly in all of them except PoE as a result. And it appears that games supporting SLI under DX12 may be the exception rather than the rule.
There's also a lot of games where the scaling is just sort of OK (~65% scaling), like Crysis 3 or The Witcher 3.
In the games where you get 80%+ scaling, it's a fantastic experience, but it's just not consistent enough to be worth it IMO.