Purushottama maas is the supreme among all months. It is special month and very dear to Lord Krishna.
Performing devotional service and austerities in this month is equal to performing 16 Kartik Vratas and therefore it is a very good time to engage in full devotional service.
The worshiper of this month will be able to burn all past sinful reactions to ashes, and after enjoying a blissful life in the material realm, he will return back to Godhead.