I randomly got the game a few days ago as a gift; and holy god do i LOVE the gameplay in this game. My character is an Infiltrator, she's a sniper with hacking capability. My current team is Ashley and the chick in the space suit with the filtered voice (Qu'rin or something?); we just had this awesome firefight in the Hangar leading up to where the alien girl who is an ally of Saren is hiding.
We opened the door and there was like 2 of those big aliens that rushes you; 2-3 robots, and one giant mecha with a rocker lancher. Me and Ashley took down the aliens my sniper gun and her awesome assault gun work; while the space suit girl stayed in the back and the nuked the fuck out of their weapons. We started to get too much heat so we retreated back into the hangar; the giant fuckoff Mecha spotted us and started launching rockets at us. Ashley got hit by one and was knocked out. Me and Space Chick were doomed, or so it seemed.
The red Mecha started rushing us, I overheated my sniper rifle trying to take him down; all hope was lost; until I realised that the mofo was just a giant robot. I went into the skills menu, selected SABOTAGE from ME and the space chick. When we got back to the action, Space chick and I unleashed the hacking furies and destroyed the mecha's shield and reapons. We then overloaded him and he was down to like 1/8 of his energy. All it took was a sniper round and the mecha was destroyed.
I really don't understand why people hate the fighting engine; it's working out really well for me right now, I havent ran into any weirdness so far, and I'm about 9 hours into the game.. I really like it so far.