I see several points points being brought up, mostly:
1. Price/Performance ratio versus previous generations (or versus GTX 1080 vanilla)
2. Memory Bandwidth is too gimped vs GTX Titan X 2016
I do hate nVidia, almost as much as Apple, but I do realize their products have their place and perform quite well in whatever role. That being said, while I myself couldn't justify spending $800-900+ for what the GTX 1080 Ti will likely cost, I am not everyone and some are willing to pay another couple hundred for piece of mind. I'm sure, if it actually does "only" have a 20% bandwidth increase over GTX 1080 vanilla as according to the rumors, 20% is nothing to scoff at. How bandwidth starved is GTX 1080 vanilla at 1080P / 1440P? Not much, if any.
Either way, the GTX 1080 vanilla is a great 1080P / 1440P card and GTX 1080 Ti will be a slightly better 1080P / 1440P card if you are able to pay the premium. I'm also certain 1080 Ti will be close enough to Titan X 2016 performance to obsolete it despite the 25% bandwidth deficiency in pretty much all scenarios short of 4K gaming.