Ranked in these QuestionsQuestion Ranking
Pro Free for personal use
Basic functionality (includes malware removal) can be used for free for non-commercial purposes.
Pro Has a portable version
A portable version of the app can be found here. It allows putting the software on an external storage devices such as an USB thumb stick and running it from there without having to install it on the target machine.
Pro Can be installed in safe mode without issues
Con Bad at removing found malware, especially rootkits
In a test performed by PCMag over half of malware that the tool attempted to remove was still running after the attempted cleanup. Rootkit removal often crashes other software.
Con Bad malware detection
In a test performed by PCMag, Spybot detected just 32% of installed malware.
Con Free version lacks scan scheduling
Premium version of the software is required to schedule scans in advance.