I just want to congratulate the Adobe team. It took a while, but 4.1 final seems to be making a great improvement in performance.
I have a fairly fast system...6 core i7-980, 12GB, Win7-64bit, SSDs, etc. However, when using multiple adjustment brushes, response times often lagged....in fact, came close, at times, to really bogg down.
No reason to complain, as I expected that the multiple RCs and longer time for final release were do to the effort to fix these areas....WELL, IT WORKED...!!!
I have test a few of my problem files and they now "fly"
So...again...thanks team....John