Ermac:
He's currently my favorite character to play as in the game. If you played Scorpion in the demo and learnt his combos, you should feel right at home with Ermac. I was able to do FP,BP, Force Lift, j.BP, Teleport Punch, dash, FP, BP, Force Push combo (about 25%+damage) after 5 minutes of playing Ermac in training mode. His enhance lift and push are excellent though his ex teleport punch is a bit lacking as it is not safe on block like Scorpion's is. His X-ray is really easy to combo. I can combo it in 2 places in the aforementioned combo. After the force lift, or after the air teleport punch. I think Ermac is a solid character for all kinds of players.
Noob Saibot:
I both like him and dislike him ... if that makes any sense. I loved him the moment I saw him in the character gameplay trailer and made it my mission to main him. Unlike Ermac, however, I don't find Noob having any flashy/long combos. I know this is a superficial complaint but I find that other characters can do a lot of damage in a juggle while Noob has to make do with 4-6 hit combos. Then again this might be my inexperience with the game.
However, the reason this might be because of his keepaway style. Noob at full screen is a BEAST! You can safely spam Shadow Tackle to annoy your opponent, since Noob doesn't travel, Saibot does. Shadow Slide to poke them if they block standing. Shadow Knee is a great anti-air, and of course the X-Ray is quick and hits fullscreen. My Noob Bnbs end with Shadow tackle and I haven't been able to find a relaunch combo with him. I think his gameplay is keepaway/combo into disabler/punish, etc. Also, he makes an excellent partner for Ermac in tag. He's decent as he is now, but if pro players find a hugely damaging combo with him, he can easily be top 5.
Jax:
Played about an hour of Jax today. At first glance, all his moves have really impactful animations. Everyone in the room goes 'F yeah' once you connect with any of his grabs. His combos are simple but do great damage. The forward lunging special is mad fast and the super armor on his unblockable X-ray really helps him out a lot. The only gripe I have with Jax is his ground pound is very situational.