AuditTrail is an excellent logging plugin with fantastic support from an enthusiastic developer. AuditTrail-Web gives a great overview to all servers across my network.
This most recent version added an overview of server and plugin versions across all servers, making it very easy to ensure everything is kept up to date. Especially useful is the ability to track plugins being enabled/disabled; easily spot incompatible plugins which have been disabled on any server.
I'm more than happy with AuditTrail and AuditTrail-Web, and am excited for the future as development continues. Using AuditTrail-Web is already making my life easier as I update and test plugins with Spigot 1.10.