I had a 2 year Bitdefender subscription until August 2007 - I never renewed. I stopped using BD in February 2007 when I switched from XP to Vista. The problems associated with BD and Vista at the time made BD unusable and I've been without antivirus protection ever since.
I just installed BD Antivirus 2008 as a trial and performed a scan, and no viruses or malware, clean, clean, clean. This version of BD is infinitely better than version 10, i.e., I can actually use it. Nevertheless, there is a slight lag in shutdown, about an extra 10 seconds, the startup has increased by about 20 seconds, even with the boot scan disabled, and I do experience slightly slower browsing but nothing significant. In short, the additional seconds are not that big of a deal.
So here's my quandary. Why should I buy another BD subscription? I've been using Vista for nearly a year without a single virus or malware. I periodically run a free antispyware scan, an online antivirus scan, etc., and nothing ever shows up. I haven't changed my computing habits in that time. I attribute my "good luck" to Vista's improved security features and, to a lesser degree, my safe browsing habits.
The question isn't a matter of cost - BD is priced very well comparatively. I'm just wondering what gains I'll receive in exchange for the slight inconvenience of relatively minor slowdowns. In other words, is it worth it to pay $34.00 every two years to slow my computer down just a tiny bit?