Surprisingly, behind the slick and artistic design, the anti-virus engine is not that good. In fact, this is probably one of the worst anti-virus programs out there in terms of effectiveness. It yields a lot of false positives (declares threats that are not there), probably in order to make sure that the program picks up all the real threats, too. For example, Immunet found that the main file of a program called USB Safely Remove, an innocent application that helps you manage the devices that you plug in your computer's USB ports, was a threat. This program has been used by me for years without any problem, on three different computers - all of which functioned perfectly.
The biggest problem is that the program precariously quarantines any file it finds as a threat. This may be a necessary precaution for files that are innocent and don't play an important role in your computer's function, but imagine if Immunet decides that some core system files of your operating system (OS) are infected. This is actually what happened to the computer it was tested on, resulting in a complete breakdown of the OS (fortunately no data was lost since the computer's hard disk drive was partitioned and only the OS partition had to be formated).
Naturally it makes sense to be cautious of possibly infected files, but if these files have a crucial role, it would be better if the user had a say in it before the program bans them from the computer. Because of its overzealous 'protection', it left my computer unable to start Windows. What good is that?