I work in a development team and we use NPM equally for basing decisions on historic trends and generating "real-time" alerts if thresholds are exceeded.
Typically we do a weekly release and it would be great for bar/line graphs to have a "compare to x" feature.
The main place I can see this being useful is on CPU and RAM
Google Analytics does this really well, allowing us to clearly see the impact of changes we make to our website on a number of variables. e.g.
pulling an image from google: http://www.kaushik.net/avinash/wp-content/uploads/2007/05/google_analytics_v2_context_from_time_sm-1.jpg
From an initial glance the below may look positive as visits has increased, but the bounce rate has increased and, the time on site and pages viewed per visit is down - so you could argue the net difference is minimal.
I think the "Site Usage" shown above would be really useful on a node level - "Node Summary", where you could see the graphs, total numbers over the period, and % difference, across all the hardware - CPU %, RAM %, Interface Usage, Disk %
Does something like this already exist (if so where is it, we are using NPM 10.7), or is anything in the pipeline?