I must admit, this is far more extensive than I had anticipated. most of these questions never even crossed my mind at all.
Dawn blade contingent not applying outside of it is an obvious thing, but so many people weasled around it.
Skysweep actually doing something is nice.
ECPA available to riptides again! YES! no other signature systems though, some could have been fun, but I'll take what I get. (puretide chip and neuroweb jammers on riptides could have been awesome)
The Eight. not a fan of the change.
Firestorm, oh my. it actually DOES work that way? I mean, its as it was written, but always felt as if the writing is a mistake.
Skywatch not coming on turn 1. bummer. oh well, not like I had any of those anyway.
Networked stealth field interactions with terrain-specific terrain is interesting.
Split fire markerlights not actually getting the bonus. was rather obvious, but good to have it spelt out.
Markerlights and jink, always played it the other way around. this will sure help against my common necron foe.
Storm of fire and pulse blasters actually works in the nasty way. return of the fish of fury?
Supporting fire flamers are always a good laugh. other armies can pull similar dumb overwatches with huge units, but nobody can quite match the sheer "utter nonsense" value of tau flamer overwatch.
Holophotons get multiple uses in a squad. HELL YEA. now just to get another ghost
(not really exited doing that conversion again would be a nightmare, and I can't have them not match...)
These are the points I found most interesting.