Hi Jez..hope your'e well mate.
I'm still mostly shooting HFT but have had 2 sightrons in the past 18 months and nikkos/nightforce/leup comp in the past. I've just set up a FT rig as i'm in the frayed knot and inter regional team this year and have to admit that i find the Sightron better than the Nikko's i've had...the sightron rangefinding doesn't wander into focus but has a nice 'snap' in, couple that with (IMHO) better optics than the Nikko and the sightron IS worth the extra cash. can't comment on temp shift yet though.
Can't really justify stretching to March and S&B cash yet......maybe after another WL. You're more than welcome to pop along to Emley on sat as i'll have the Sightron with me and there should be a couple of Mk 2 and 3 Nikko's kicking about.