I managed to roll spec enough times to try them all and they are pretty great.
SADAR:
Deletes xenos.
Great, always has been.
Demo:
Stunlocks xenos for teammates to delete.
Great.
The airburst nades offer fun variety and lower teamfrags. Nice.
Sniper:
Ability to cloak and the power shot are great improvements.
Lots of fun to play.
Scout:
Major improvement with cloaking being much harder to see.
Use to just be a normal marine with a better gun and a Jtac kit (before jtac kits were a thing).
Now can genuinely get behind enemy lines and do fun stuff.
Pyro:
Use to be the worst spec.
Now it's doing much better, bluefire seems a lot stronger, green is great for stopping xeno pushes.
Firewalking is a much needed improvement.
The weapon it's self is not intuitive though. I put a green fuel canister into the pyro backpack and I thought it bugged out and vanished because the pyro backpack inventory was empty afterwards. So I put the rest of the fuel in my pouches. I tried to attach the flame canister to the flamer (like SL's flamer). It popped off after firing the first shot and I died trying to pick it up and put it back in to fire again.
Pyro spec really needs an instruction manual with the kit lol.
Great improvements all around.