yeah Norton 2010 is good - really quick compared to previous versions. Doesn't affect computer tasks at all, unless doing background scanning. If you want to go back to what you were doing before without the background scanning hogging your CPU, you can just right click on the Norton icon in the system tray and select silent mode. Don't really have anything bad to say about it, recommended from me. Think PCAdvisior have a review of Norton 2010 somewhere..
Changed from McAfee to Norton I.S. 2010 in January. Seems fine. 2 minor annoyances - you can get really annoying popups at the bottom rh corner of your screen telling you that Norton is "performing background tasks" rather too often - although this has decreased recently on my pc's (an animated system tray icon like McAfee's would be much better - less intrusive); also there is no % complete readout when doing full scans, which McAfee had.