If it is active when you go down, (green devastator mode graphic tells you it is) the repair matrix will revive her. The revive removes the effect, so you have to use the skill again to get revived again. But assuming you have 'grenades' you can use it as much as you want.
I definitely dumped fitness on her, she has 750 base shields and with the shocktrooper upgrade, it was easy to keep up her repair matrix any time she was under duress. Tried her with the Claymore (destroys everything) and Reegar (destroys everything faster, that gun is totally busted). Opening from cloak with snap freeze gives you a reliable stagger against multiple enemies, making it easy to line up headshots (not that you need them). She is easily among the top 5 kits in the game, and is by far the easiest of the new ones to use, because for all her tricks, she's still a shotgun infiltrator, which is far from new.
I also had a lot of fun with the Juggernaut, Cabal, and Collector. I'm not huge on the other two, though I hope I'm just not 'getting it' where they're concerned.
As for the new weapons, I've got at least 1 level in all of them but the Punisher, and I'm really liking the lancer. The venom shotgun, I just don't get it. I need to see video of someone using it effectively or something.