GFI (formerly Sunbelt) Vipre Antivirus 2011 ($30 for one year, one PC, as of 12/18/2010) finishes tenth in our roundup of 2011 paid antivirus software. Vipre is the epitome of the expression "mixed bag." It detected known malware well, cleaned up after infections competently, and it's reasonably speedy. But its design is cluttered, and it struggled mightily at stopping brand new malware.

Installing Vipre Antivirus 2011 is reasonably straightforward, but it does require you to restart as part of the installation process--a slight annoyance . Vipre's main interface is generally clean, but some important information gets lost. The scan button, for example, seems to blend in with everything else on the screen. The overview pane provides a decent overview of your PC's protection status.

The settings window feels cluttered, and it's hard to understand at a glance. Some of the copywriting needs work--the wording may be unfriendly and overcomplicated for some users. But on the positive side, each tab has descriptive text describing what the settings are for.

Vipre Antivirus is an inconsistent defender: It did perform reasonably well in detecting known malware, finding 97.9 percent of samples. This is a good score, but behind the top performers, which managed detection rates of over 99 percent. Vipre also did a serviceable job at disinfection: it removed all active components 70 percent of the time, and removed all malware components -- active and inactive -- 40 percent of the time. These, again, are good scores, but not quite up to what top performers managed (top-scoring products removed active components 80 percent of the time).

It didn't fare as well, however, in "real-world" detection tests that show how well an antivirus product can block brand new malware. It fully blocked only 60 percent of malware attacks, and partially blocked an additional 16 percent. This was well behind the average full-blocking rate of 83 percent, and placed it at the back of the pack in this test. No product we tested fully blocked all samples, but Norton Antivirus 2011 managed to fully block 96 percent of attacks.

Vipre also had some minor false positive issues, flagging six good files as potentially malicious, but the overall rate as a percentage of the files Vipre evaluated was still quite low.

GFI claims that Vipre won't slow down your PC, and in this case it delivers: It had one of the fastest manual "on-demand" scan speeds among the products we looked at for this roundup (1 minute, 41 seconds to scan 4.5GB), and it was reasonably fast in on-access tests that judge how quickly it can scan files as they're opened or saved, scanning 4.5GB of files in 4 minutes, 20 seconds. And its impact on overall PC performance was quite low, completing most of the speed tests we put it through with faster-than-average times.

If GFI can improve Vipre's blocking of brand new malware, and put some more effort into the interface, it could become a contender. But as it stands now, though, we can't recommend Vipre Antivirus 2011.