I had 5690 for 1 year and half.
I really liked it except the heat and poor hinge design.
When I playing games like CS, my left hand get sweat. I always worried about hinge when I open and close lid.
noise level - very quiter at idle. when it start to kicking, its just same.
Heat - its acually cold at idle. 30c right now.
when gaming, it goes up to 55c. right palmrest is hotter than left side which is good. its just warm not hot. i can put my left palm all day.
Do you like your 5670? if so, you will love 5720.
What I felt about both is Beautiful, lovely and fast laptop.