So far, I like moat of them. Only the Ace sig abs have left me cold.

Ace is very specific uses. "This one is mine" is just like "Fated Duel" except for vehicles. "Unmatched Survivability" lets you take the tissue paper fighter you have, and keep on going. Admittedly, you will need to be fished out of the deep dark afterwards, but the same can be said for any good berserker.

Unmatched Expertise.

It is just that good...

I don't like effects and abilitys with the title "once per session" in general. I would prefer weaker abilitys that can be used more often.

The Signature Abilitys are nice to have but not cost effective in my oppionion. Last man Standing is nice, but a character with a jury rigged auto weapon and a solid skill for the weapon could do the same easily in one or two rounds without the need for this ability. And i am not fond of this kind of story altering tricks. Either the GM wants the Group to get away or do this or that or he doesn't.

Our Group plays on a weekly basis and a session lasts for about 8 hours and can cover weeks or even months of ingame time if long hyperspace travels are part of the story. So less powerful but more useful abilitys which could be used on a daily basis would be by far better in my oppinion. There is no logical reason why a Heavy shouldn't mow down a bunch of stormtroopers when fleeing on a spaceport and using the ability again when boarding a starship full of pirates two weeks later in ingame time, even if the flight was handled in 5 minutes play-time.

The other option would be to break one evening of gaming in a few gaming sessions as far as the rules are concerned.