The testing ability. The builtin Javascript libraries. The ease of adding transformations. The ease of database read and writes for HL7 messages. The varied destination and output options. Review collected by and hosted on G2.com.
There does not seem to be a native Excel format source option. Converting Excel to .csv and then using it is a work-around. However, this adds another step in the process. Review collected by and hosted on G2.com.