Real-time protection in security suites always consumes resources. McAfee did a reasonable job in not overly stressing test workstations with McAfee Internet Security Suite 2008 installed and functioning. Task manager shows several McAfee processes running, each starting with an 'MC.' [See image 20]
The default settings for anti-spam integration in Outlook were not reasonable. It scanned the inbox and then moved many messages to the McAfee antispam folder and affixed 'SPAM' to those messages.
Also, as with any protection application, it's only as good as its effectiveness in protecting the workstation. McAfee has been around a long time with antivirus and other security products. They do a reasonable job in providing updates and staying current for users.
The complete installation worked well on Windows XP with Office 2003; however, it was a bit of a battle on Windows Vista with Outlook 2007. Several errors were found and missing prerequisites had to be installed after the application.