I'm the dissenting voice!
Long ago, an MS update hosed my machine. Since then, I look at MS updates before I install them. If it's updating something I don't have (such as Office 2007), then I tell it no. If it's the MS monthly "spy on your computer" update, also called WGA, then I tell it no. Otherwise, mostly yes.
Avast updates at whatever frequency Avast set as default, but it's several times a day. It does catch a lot of nasties in incoming e-mails, too. With that, and WOT on Firefox, I'm constantly reminded what a dangerous place the Internet is.
Spamcop these days takes 95% or more of all my incoming e-mail and correctly puts it into the spambox. If there were a way to stop spammers using the Internet for their own silly purposes I'm sure the service would improve for the rest of us.