As far as all of my use with the Sig 35 is concerned it is the most consistently focusing lens that didn't need any AFMA for. My Canon 50mm 1.4 fails consistently though, I can never get it well adjusted as it behaves differently at varying distances, and the whole part about it not being sharp and all the CA and PF. Meanwhile, just last week I dropped my Sig 35 onto concrete, and I'll have to send it in (hopefully warranty will cover), but it still works perfectly!! Just really tight getting it on and off the camera. I'm impressed with Sigma and will be looking forward to their future releases.
But if there's an offer out there for a 35L around $900 then shoot, take it, you'll be guaranteed to get close to that much back in the future too