A little too splenetic but a valid argument nonetheless.
Well, my point was that, a person's choice of games differ from person to person. There are people who cherry pick SLI enabled games to make full use out of both cards they spent their money on (the letting hardware decide their game bunch), and perhaps those are the ones that experience the better side of SLI. Then there are those who don't care whether they support SLI or not, they want to play it, so they play it, which then finds out that some of the games might not run in SLI at all (EG Doom), or causes issues when running in SLI mode, which sours their perception of SLI.
I am one of the latter, hence my experience with SLI soured. That, and the fact that the way I setup my rig doesn't allow for SLI unless one of the cards do not come with a backplate (AFAIK only a few 1070 don't have backplate, none of the 980ti or 1080 doesn't have it).
Ironically, I chose SLI not due to the average scaling of SLI, but rather I chose SLI because I can tolerate the performance of a single 970 under 1440p, at the time that choice was made. The only game I had which both didn't support SLI, but could do with it under some cases, was Wolfenstein.
Another thing about SLI I don't like, is the degree of uncertainty. The uncertainty of mGPU support in the near future, given what we know about SLI support of games as of late, plus the fact that we know next to nothing about how EMA works under DX12 (what little one can find on the net about it doesn't paint a pretty picture either). It could very well be awesome (and I do hope it is awesome), but it could also flop badly.
I simply find that, given what we know, and what I want, mGPU is a decision that is best made when substantial number of DX12 games comes out (such that we have a better picture of how EMA really does), not at this moment in time.
I do agree with WorldExclusive on one thing at least: I wouldn't upgrade to an 1080 if I had 980ti SLI, if I find a single 980ti being enough (by most accounts, it is).