I tried out 6.90 RC3 the other day. I found memory usage was much higher than 6.82.
I generally keep 3 watch groups open. One of them is quite old and I switch the Display Age dropdown control to the current month. In this case it is "21: October".
In 6.82, Process Explorer showed the memory usage as:
Virtual Size: 5,912,080 K
Private Bytes: 1,421,568 K
Working Set: 43,512 K
In 6.90 RC3:
Virtual Size: 20,281,312 K
Private Bytes: 15,741,660 K
Working Set: 7,893,244 K