I was with Trend Micro PC-cillin for about 6 years, after I dumped Norton, {Norton = bloatware, and too expensive, and let viruses in, and it's very hard to get rid of!}
I got on okay with Trend, but... one year the official upgrade wrecked my PC and I had to spend a whole afternoon on the Trend helpline just to un-pick the messes the Trend upgrade had made! (they privately admitted they had messed up!
Also, the Trend company don't seem to respond very well to customer needs. And too, (as another reviewer points out here) the downloads of latest updates is **very intrusive!** I tired telling Trend about this, in one of their 'feedback' enquiries, but of course they did nothing about it. ... Who, -after all, needs a *very large* / intrusive splash screen suddenly appearing right in the middle of their pc work, just to let you know the prog is doing something? NOD is much more discrete, take a leaf out of their book Trend Micro! --or you stand the risk of losing previously loyal customers like me.
Btw: re catching bugs on the Internet, the Trend product did seem to be reasonably proficient, but lets itself down in other respects.
Footnote: I finally opted for Kaspersky 2010 suite as my new AV+ firewall, then regretted it when it conflicted with traces of another prog. Ho hum!
(NB: see my separate review of Kaspersky 2009 / 2010 on this site)

Just use It.
You Can't Find any better Anti Virus than Trend Micro PC-CILLIN Internet Security 2007

I got PC-Cillin FREE on a 12 month license with a motherboard I bought a few years ago. It seemed to work OK, so I signed on for a second year (about £25 if I recall). This did it's job fairly unobtrusively and even found a virus occasionally. I built a new PC towards the end of last year and my license for PC-Cillin was due at about the same time. I saw a special offer of a 2 year license on their website for £40 so went for it. It downloaded OK, and I set it going to install. Bear in mind that my PC was brand new and the version of Windows XP had a registry that was positively virgin. The entire program failed to install properly with all options. I tried to uninstall it and it failed. I tried to reinstall it. It failed. I emailed their tech support. THREE WEEKS later I got a reply asking for my entire Installed Programs list. In the mean time, I stumbled on a utility on their website to "manually" remove their products. This basically hacked entries out of the Windows registry with a blunt spoon so that your PC thinks it has never had any of their stuff installed in the first place. However, it didn't find everything and I had to set about the registry myself.

The reply I got about a week later suggested I use the uninstall tool. By this time I was getting quite cross. I emailed again. Waiting, I tried to install the software with only the basic Anti-Virus stuff and none of their new Spyware and Email protection stuff. Funnily enough it worked first time. I eventually got a rather plaintive reply from Trend suggesting I not use IE7. This made me furious as the version of software I had was released AFTER IE7 came out on the Microsoft Update site and removing IE7 from a Windows install gives even techy people a headache. I asked Trend where this "feature" of incompatibility with IE7 was listed and they pointed to their "requirements" list which states something like "A windows based PC with Internet Explorer 6" - written before IE7 was available. Nowhere on their entire website does it say "don't use IE7" In frustration I asked for a full refund and a cancellation of my product license. Two weeks after this, I got an automated email from their server telling me my support call had been closed. So, unless I either buy another Anti-virus suite or reinstall XP and try to "only use IE7" I'm stuck with this package.

To add insult to injury, even though the software seems to catch the occasional virus, it usually wants to update when I am in the middle of typing something, so it gets in the way. Striking certain keys in mid-flow of a sentence closes the window and you have to re-run the updater manually. It is also incompatible with Half-Life 2, and indeed any products running Steam, so if you want to play online, you have to turn your virus killer and Trend firewall (PC-Cillin doesn't work with the Windows firewall on, it requires its own!) - at the exact time when you're probably most vulnerable to teenage hacker geeks. On top of this, the scheduled scanner ignores whatever I tell it and seems to have a habit of popping up at random when I am watching a DVD or playing a game on my PC, making the related software crash.

In summary: DON'T WASTE YOUR MONEY ON THIS RUBBISH