QUOTE(danny_sp15 @ May 29 2011, 07:58 PM)
grade assist is to assist when starting on a hill. it will hold the car for a few seconds when u're starting uphill. good for new drivers, i usually just hold brake with left foot, and build rev with right.

That's Hill Launch Assist (some call it Hill Hold Assist). It kicks in when the gradient is 3% or more.
Gradient Assist is that little button on your gear stick. Not sure how to explain it though other than quoting websites.
Popular Mechanics describes it as "designed to eliminate autobox “hunting” for the right ratio on steep roads."
Emotormag calls it "In addition a gradient assist function can be activated when climbing steep gradients where there may be a tendency for the transmission to continually shift between gears. By activating a button located on the gear lever, it allows for improved drivability in hilly terrain."
But if based on driving feel, upon activating gradient assist, the RPM goes up and you get more accelerating power when driving uphill. Tried this on Karak highway during my trip to Kuantan. Without GA on some really steep climbs, acceleration feels slightly sluggish but when GA is activated, you can feel the acceleration power suddenly kicking in. I have only used GA when climbing up steep roads since I think that's where the name Gradient Assist comes from. Plus, using GA on flat roads will be detrimental to FC due to the high RPM. Never tried it on downhill motion though.