I'm using BidDefender. I got a 4 license package for $65. They update their virus definitions usually a couple of times a day. They have one of the best response times out there for virus updates. That being said, it only runs flawlessly on my 3.2 ghz P4 640 w/ 1 gig memory. It runs nearly perfectly on my P4-based 2 ghz Celeron w/ 1.5 gig memory (only observed dificulty here is a slow full system scan, due more to the crippled nature of the Celeron chip than the BD program). My AMD K6-2 at home and my P3-based Celeron laptop couldn't seem to handle it without SERIOUS problems (by serious I mean corrupting the system and config files requiring re-format).
Final verdict: If you have a newer system with plenty of memory, the features, price, and virus updates make BitDefender one of the best out there. If you have an older system, stick with something else.
Also, check out
firewallguide.com for good info and comparisons. They cover spyware, anti-virus, as well as firewalls. TONS of good info there.
Edit: It is possible that my system problems w/ the AMD K6 and the P3/Celeron laptop came from conflicts w/ other security programs. Spybot, AdAware, and NetVeda Firewall were all running on those systems too. I've not re-installed the BD on the K6 yet, and the laptop is still dead due to no functioning CD drive for reformat. So at this point it's uncertain if the older systems just couldn't handle BD, or if it was conflicts that caused the failures.
