Reconnoiter - Anyone using it?
The really neat thing about Reconnoiter is that graphs are effectively pointers to the metrics they contain. There's no archaic concept of rrd database files for each graph, just a JSON object describing the graph.
There is a learning curve with installation and setup of Reconnoiter, which may be a drawback. Alternatively, you should check out Circonus (http://circonus.com/), which is a hosted service built on Reconnoiter, adding in fault detection and notifications. They have videos up on the site.