If you mean things like ClamAV and the other host of scanners, then here is my take on it.

ClamAV, has signature updates out sometimes a day faster than Symantec or McAfee. sometimes when Symantec or other commercial scanner have it first is because they were the ones that found it. Most of the time ClamAV gets the updates out within hours of the release by the other parties.

Some Open Source products have fixed 0-day exploits seen in the wild, on 0-day. Symantec has never done nor will it do that.

Try to get these huge corporations, in fact, I'd truly like to see you really get anywhere with those SLAs. It is all crap. Sure lawsuits happen over SLAs, but the damage was done, the time for it to be effective came and went without it being effective, its all spilt milk by then.

SLAs on Software are so ridiculous. How about trying to get Microsoft to do SLAs on Windows... don't make me laugh.

Just for the record, in my setup for "work" I am using CalmAV, SpamAssassin with Rules-Du-Jour, DCC, greylistd, pyzor, Vipul's razor, Exim v4.62, Courier pop3/pop3s and imap/imaps and maildrop. And on the Windows machine I am using AVG Enterprise (cheap and better signature update times, in every event I have seen so far using them). I am only using AVG for Client protection. Server protection I am using the ClamAV vfs add-in for Samba and ClamAV on the Mail-side. I have had one virus in get into the Windows machines but not the network (barring the Internet Explorer HOLES the size of New Jersey), in 3 years. And then it was actually from an Infected File on a CD. The updater for ClamAV (freshclam) is configurable to do things in a number of ways. Very flexible. Same thing goes for AVG.

Of course all of this is for the Windows side of things. I get all those virus messages in my mail clients, except they can't execute, and are stopped dead in thier tracks. I use LeeNoocks OoperAteeng Sistern. Basically, I'd have to be STOOOOOOPID to use root as my user. Nope, plain ole, plain-ole user for me TYVM.

So, if anything gets toasted, it is only my junk owned by my plain user. That is what backups are for anyway.