I work in the industrial/process control network security field. We'd never deploy MSE to a client site, since it lacks central management features and remote deployment capabilities, but a lot of the guys on my team (myself included) use it on their personal computers. It's on my laptop, and it catches pretty much everything I throw at it.

Best of all, it's impact on the system is minimal; most other free A/V solutions can't compete with it in this regard, and put a heavier load on the system.

Oh, and AFAIK, there is a way to opt out of sending stuff to Microsoft; in the MSE Settings pane, set the Microsoft SpyNet setting to I do not want to join SpyNet.

Recommended pairing: Malwarebytes Anti-Malware. Run a scan with this once a month, and a scan with MSE once a month, and you will probably have to work really hard to get a nasty infection on your PC.

Not used it, not convinced it's any better than avast!, to be perfectly honest with you. McAfee is crap though, stay well away.

I use that on my laptop along with spybot. I alternate between using the two spyware checkers.

My desktop has avast! which I prefer but it's practically a toss-up. MSE has a slight edge over avast! in the resource usage department.

Both Avast! and MSE are excellent virus scanners.

I use it, and like it well enough. I used to use AVG Free, but MSE seems to perform a lot better on my system. I cannot vouch for how well it can clean an infection since I haven't had one. It did successfully detect and isolate some malware once, so I figure it's working effectively.

A friend's netbook was actually infected with AV8.exe and had to help him install malwarebytes and MSE to flush it out. Was extremely surprised that there was continual infection detected afterwards and that MSE was able to detect some of the various trojans. But still felt unsatisfied that it could not clean up everything after a major infection. Or that it still is uninstalling major infections. The problem is after experiencing MSE from that friend's netbook, I still trust my mainstays: spybot, comodo, and avira. Together, they seem to have a better rate of detection, protection and cleanup after infection, known or unknown.

I think the major point to underscore here is that there really isn't an A/V solution which can boast a 100% detection rate. I'd argue that among paid solutions, NOD32 is really about the best thing money can buy...and I've seen it let things get past it (though not many, admittedly). AVG has let me down in the past. Comodo has too. MSE hasn't let me down on my laptop, though the XP version let me down on my wife's desktop PC and let a particularly nasty rootkit slip past.

In the end, there is no one sure-fire means of defending against malicious programs of all sorts. Mature, informed, and somewhat skeptical-by-nature use of a computer and its software is pretty much a must these days; even the best A/V program out there can be defeated by someone using a computer stupidly.

For those wanting a secondary scanner to fill gaps in your current protection, check out Hitman Pro. Scanning is free (as is deletion of tracking cookies). It can catch a lot of things other products might miss.

If you have a major infection that your current security product didn't stop by itself (e.g. a rogue antivirus taking control of everything) I'd strongly recommend restarting in Safe Mode (hit F8 during boot) and using System Restore to go to a restore point prior to infection rather than actually trying to clean up its effects with another security product. All but the nastiest infections can be removed or at least rendered inactive by System Restore as long as you have a restore point prior to its arrival. You can then scan for any other goodies hiding around, make a clean restore point, and finally delete the other restore points via Disk Cleanup. This saves a lot of time, and if you don't have a restore point far enough back or it doesn't do the job you still have the option of scanning for it the hard way.

MSE is only licensed for small businesses (up to 10 computers). For larger businesses and/or more advanced management there is the business equivalent, ForeFront Endpoint Protection. There are also products in the ForeFront line for servers and networks and such.

I switched to it from Avast when that started to seem a bit bloated and inadequate. So far I haven't been disappointed. But then it hasn't really been put to the test yet either.

I may be hijacking this thread a little, but I would like to add...

I use AVG, and ZoneAlarm, but they have not proved half as useful as Secunia PSI (free). The majority of viruses will target a vulnerability in software, so if you use such a tool to keep you software up to date you are way better off. In short, stay above the water line for virus attacks. As for which security package is best - I hear a different review every week, they are all pretty good. they're going to catch 99%, I'm thinking of moving from AVG simply because it keeps popping up its adverts.

I already do that. :) I run uTorrent in the Sandboxie program, scan once a week with Malwarebytes and once a month with Emsisoft Anti-Malware. I also switched from PC Tools Firewall since it is now obsolete and no longer updated to the Comodo Firewall and while it's more of a pain to work with it's a stellar program. I also run Immunet Protect as well as a 'cloud' antivirus with no performance impact whatsoever. Found 3 worms in a download I had and I love it.
I use Secunia PSI and the online version as well.
I don't know about that. Norton was GREAT when it first came out (So I've read, but now it sucks horribly.) and there are even cards you can buy at the nearest store for McAfee and Norton as well. Security software is just plain annoying, but you need it. Thankfully I have had no problems at all with my laptop.

It's fantastic. It's lightweight (relatively) and free, and does everything I want like not bothering me unless it's urgently important. Don't know how well it works at disinfection but at least it does detection alright.

The only thing I really dislike about it is that it takes approximately FOREVER to do a full scan.

Norton was great, then it became a heaping pile of garbage, but now it's great again. The problem is that so many people have been turned off by the mere mention of Norton nowadays that they automatically assume it's still awful (I think they should have changed its name to Symantec AntiVirus/Internet Security or something).

Basically if you have Norton 2011, Kaspersky, or NOD32 you should be in pretty good shape.