Is the 1070 Ti still worth it?

While the 1070 Ti might be worth the investment now, that could very well change once those miners start buying in droves and drive the price up. At that point, opting for the original GTX 1080 might become the best option.

Is a 980ti better than a 1070?

Since GeForce GTX 980 Ti offers significantly faster memory than the GTX 1070, if you want to use the graphics card in applications where the memory performance matters a lot, GTX 980 Ti might be able to outperform GTX 1070. GTX 980 Ti has a memory bandwidth of 336.6 GB/s while GTX 1070 has a memory bandwidth of 256.3 GB/s.

What is better 780ti SLI or 1070?

SLI is horrible and even if it would work, the 1070 will be faster or close to the pair. I second this. 1070 is absolutely the way to go. Thanks for your input! SLI is never a thing that you do "down the road". You do it, because there's no single GPU solution that is better than what you can purchase currently. Its weird that my 1070 has sli.