You might want to postpone downloading that latest OS X update. According to David Passell it is reported to contain an out-of-date and vulnerable Adobe Flash Player. You can read the full story here. David says, "I installed the update, and I believe the machine speeded up in its responsiveness. I haven't yet gone to the Adobe Flash Player site to get their latest as advised in the article."
Today David adds, "I don't think postponing the OS X update is necessary. However, after doing the update you should go to the Adobe web page and install the 10.1 update."