You should consider the following aspects before making a decision to use Apache Mahout as your machine learning library:
Are you looking for a machine learning algorithm for industry use with performance as a critical evaluation factor?
Are you looking for a free and open source solution?
Is your dataset large and growing at an alarming rate? (MATLAB, Weka, Octave, and R can be used to process KBs and MBs of data, but if your data volume is growing up to the GB level, then it is better to use Mahout.)
Do you want batch data processing as opposed to real-time data processing?
Are you looking for a mature library, which has been there in the market for a few years?
If all or most of the preceding considerations are met, then Mahout is the right solution for you.