Review on Key Metric Software by Kevin Zamora

I like that it's free for personal use with no limitations to number or size of computers monitored (it works well in our small office).

It does not give you any metrics about what percentage your users are using vs how much they're storing/transferring via email etc - which other solutions do offer as an option but at additional cost? We have been able solve some storage issues by monitoring file sizes across multiple devices rather than just one computer where we would normally expect most data growth to occur!