The 35mm f1.8 got a great review on Lenstip. Less vignetting than Sigma art, had IS which Sigma doesn't have, focuses to 0.2 meters, and its a half pound lighter and more compact than the Sigma.
Tamron is bringing back the SP primes, and that is good. Tamron 35mm sells for a couple of hundred less than Sigma.
I have no feedback for how it works with the Canon Metabones IV to Sony E adapter for AF.
Its a new lens and nobody is giving it a discount yet but its still a bargain.