FirstAdopter.com points to a CNET News story today:
Starting today Microsoft is going to use Trend Micro instead of McAfee for anti-virus on Hotmail. The reason for the change is unclear although an Austrialian Microsoft executive said Trend Micro’s products offer “deeper virus protection.”
Excellent move. I don’t recommend McAfee software at all, and I am an enthusiastic supporter of Trend Micro. I use Pc-cillin Internet Security 2005 myself. I’ve installed this package on several clients’ machines in the past year and have heard nothing but positive reports. If you follow the link (I have no relationship with Trend Micro and get nothing for the referral), note that you can save some money by choosing the Upgrade option ( you qualify if you have any AV software at all). If you have multiple computers, check out the Home Security Pack, which is an excellent deal.
Ed Bott 
I use McAfee VirusScan Enterprise, which is free from my university since they have a site license (and it also means that the campus network isn’t affected by worms and viruses). It’s pretty good – non-intrusive and responsive. Obviously though it’s aimed at enterprise so it’s out of reach to the home user.
It’s certainly better than Norton which annoys me immensely.
I personally love (and use) Trend Micro. Their latest version (2005) gives me the option to install only the antivirus program itself, without the additional bells and whistles (e.g. firewall, anti-spam, and other additional programs I may not need or want on an up-to-date XP SP2 system with Windows Firewall). Unlike, say, Norton’s antivirus program (or Symantec products in general), Trend Micro has no transparent effect on system performance or resources.
Also, I have had very bad experiences with McAfee. I’m not sure why –McAfee has been around for years and presumably most people who use it have done so without major problems. But I am certainly not the only one who won’t allow any McAfee product on my computer (at least not unless it is thoroughly backed up).
I am no longer a fan of Symantec products, although until a few years ago I was a big fan. My personal opinion is that they now market internet security for dummies, sacrificing performance for lots of security bells and whistles that experienced PC users simply don’t need. For example, their firewall is much more intrusive and protective than the Windows firewall that comes with SP2, because it prevents trojans and worms from “phoning home,” i.e. it blocks outbound communications other than from authorized sources (which the native Windows firewall doesn’t do — it blocks unauthorized inbound communications only). But here is an even better idea: just don’t let the trojans or worms from getting on your machine in the first place! Well, duh! That way, you have a clean machine plus a firewall that imposes a much lower strain on system resources and performance.