It depends on how you see it. While it's likely the 1070 won't perform at its absolute best, with GTX 980 and 970 SLI setups running fine on X58, I doubt you'll be disappointed by its performance. It's what I'm planning to plant into my X58 once the prices go down a bit and manufacturers throw...
Let me also share my X58 related experience with you.
I am still rocking an now ancient i7 920 C0/C1 on a despicable Zotac X58-SLI-A-E motherboard (probably one of the weakest and most problematic X58 implementations - having no real OC capabilities and tons of issues with RAM, no Xeon support...