After weeks of reading all the Symantec bashing on here, I feeI I need to share my experience with NIS. I installed NIS 4 for Mac on the update launch date and immediately within installing, LiveUpdate downloaded compatibility updates for SL. It's been a couple of days now, and so far so good. Note: this is the FIRST install of Norton software on my mac, if that makes a difference. NIS has not slowed my system down, web pages and applications load just as quickly as before, my mac boots up within 14 seconds from complete shut down.
Thanks to Norton/Symantec for making the setup process clear and simple, just like Norton software on my old Windows PC! 
In waiting for the updates to Norton software for SL, I was using trial versions of Intego Virusbarrier and Netbarrier...although Netbarrier does seem to have some advanced settings, I found the setup of Intego's firewall to be CONFUSING. NIS for Mac has that learning stage that Intego does not, so I know the Norton firewall is actually working and asking to grant applications permission to access online.
Yes, there was quite a delay in getting this update out, but at least Symantec is testing their software in getting it ready before release. Keep up the good work!