When I purchased my tab2 in September, and turned it on, it mention the update. I let it update the tab, so at that point, I hadn't used it to really know if it was a good or bad update. AFAIK, mine is running really well, no issues that I can see.
I'm now waiting on 4.1.1 or whatever it will be, but going to wait until it has been out a while before updating mine.