Bitdefender internet security is a pain in the ass, not only it slows your computer down, it installer size is gigantic, antivirus alone already 2xxMB in size...gaming performance will be totally impacted, so be prepared to get 2x-3xFPS or lower when using this security suite... last time I always thought my computer system not supported the game with high resolution...but actually bitdefender caused the slow down!! Uninstalled it, and all my games runs so smooth...
They released 2011 version, tho they have fixed the issues...but NO...still lag your computer as well, and much more bloated now

..will never touch bitdefender and totally not recommending this suite at all...pretty good detection..but at a cost of your computer performance...not worth it, better spend on other suites.
panda nowadays also becoming much more like.."everything is malicious"..even flagged those openvpn as malicious, and some other programs..and caused problem in displaying sites...
avira 10...performs not so well compared to ver 9..i don't know why, it seems much more malware went undetected...weird
nod32, never tried this before..
kaspersky is 2010 - ok, 2011 - don't know..but i read some comments that kis 2011 slowed their computer down..
nis - so far ok, but there's some issues also..like "love" to get conflict with some of the firefox addons, and certain stuff..really annoying..
tried f-secure is..installed, slowed my boot time to desktop..and caused me unable to use the desktop for like 5 minutes..straight away uninstalled it afterward..
g data - i heard this one also will bloat your computer performance...much like bitdefender case...
comodo - only use it if you know what you're doing, totally not for first time/newbie to the internet users.
i mostly will install those separately, like using MSE/Avast [either one] as the AV, and comodo as the firewall...