Recs.
Updated
Mixpanel is a very popular, event-driven analytics tool. It supports all the features a SaaS web-app would expect as well as some killer additions such as "engage" that lets you use your analytics to send highly targeted emails to your users and the ability to see completely live data.
Specs
Pros
Pro Behavioural messaging
Mixpanel allows you to send notifications based on users actions. For example, you can use it to improve customer retention by analyzing the conditions where your users decide to leave your product and then send targeted messages designed to bring them back. This is an amazingly powerful feature that really bridges the gap between analyzing the data and acting on it.
Pro Easy to use web interface
Online interface makes it simple to view events, and aggregate data.
Queries can be built by selecting actions and associated properties from a drop-down, and the corresponding data will be displayed. These queries can then be bookmarked for later use. A table view and CSV export option is also available. Multiple queries can be displayed together, making it easy to compare two sets of data, or to view the relationship between them.
The interface also features a "Live View", allowing you to watch events as they are sent, which is useful for testing, and viewing realtime events.
Pro Contact users directly through the people page
Mixpanel allows you to directly contact users from the people dashboard via push notifications, sms, and email. After viewing the user history, or filtering on events and metrics, you can send an individual user, or a segment direct messages.