I've had bit defender 09 and 10 and had zero complaints, until my subscription expired, then I was inundated with pop ups that froze my pc plus my wifes, which caused all sorts of unwanted noise.
I installed 2011 and I think this is horrible, slows my computer way down then it froze my computer during start up. I had to go in to safe mode and stop bitdefender from running.
Without bitdefender, my computer is now running great...this new program is a mess.