yes - but its not a simple "you can't see me :3" type deal. invis erases you from radar and kinda sorta makes it harder for people to react to you. you're not going to be able to walk up on someone expecting to see you.
however, with the blade dancer invis crouch thing. what worked great for me was to crouch for the 3 seconds to go invis then sprint and jump through entrances wherever i expected people to be at while staying as high as possible. people never expect it. they never see it. and without radar its impossible to plan for really.
neither - better control. triple jump is useless really. i don't think people realize how much your aim turns to crap in the air.