I am just curious, is rainbow tables any use for password auditing?

I do not want to crack all the passwords but do want to check if they are secure, and reveal the unsecure ones which I am using John for at the moment.

Maybe generate some alpha-numeric tables only and use Cain?

What types of auditing could I do with SHA1 tables? I am looking for practical applications on how the different types of tables (MD4,MD5,SHA1, etc) could be utlized for auditing if possible.

Or am I wasting my time and should just continue use John with some good wordlists.