Just a quick straw poll... which components do you leave on via your policies and what effect do they have on your machines? There's a lot of mention about "Self Defense" in the threads but I've turned off Proactive Defense as well... generates a lot of false positives and I reckon could also be a slowdown factor as our machines feel quicker with it off.

Here's my list and why they're on \ off

File AntiVirus - enabled
Anti-Spy - enabled (Anti-Dialler on, popup blocker already in Windows so no need for it twice with Anti-Banner)
Mail Anti-Virus - disabled, we've got MessageLabs doing that on the mail feed so no need to check twice
Web Antivirus - enabled
Anti-Hacker - disabled, conflcits with Windows Firewall as mentioned in manual installation (?) so we stick with Windows Firewall GPO controlled
Anti-Spam - disabled, already with MessageLabs there
Proactive Defense - disabled, too many false positives, very twitchy and possible performance implications?
Device Control - enabled but nothing blocked, does block autorun which is good though (although that's controlled via GPO anyway)

Copy / pasting - This is what we're testing in our MP4 policy.

File AntiVirus - enabled - obviously
Anti-Spy - enabled - enabled but users can add their own white/black list.
Mail Anti-Virus - disabled - KSExchange running on servers.
Web Antivirus - enabled
Anti-Hacker - disabled on LAN, but enabled when mobile
Anti-Spam - disabled
Proactive Defense - enabled with Registry Guard only. App analyzer is too much of a performance hit.
Device Control - enabled but nothing blocked aside from autorun.inf.

So far so good. Doing a lot more internal testing of this version on XP/Vista/7 before pushing to clients.

Currently on 6.13 I use the following

File AntiVirus - Yes
Anti-Spy - Yes
Mail Anti-Virus - Yes
Web Antivirus - Yes
Anti-Hacker - No GPO controlled with windows firewall
Anti-Spam - No controlled at perimiter
Proactive Defense - Yes but will check this with mp4
Device Control - Not on 6.13 but doubt will use this feature as controlled via GPO

About the same as everyone else here.
No Anti-Spam
Anti-Hacker client by client choice.
Proactive Defense has been fine for use.

Good to see you already found out about that nasty Self-Defense this on MP4.