I've done a lot with server performance stats but one of the things I've not found is an easy way to see average, minimum, and maximum values for a performance counter for a time period. Here's some code that'll help you get these stats (without starting from scratch).
In the past I've resorted to playing data back using the historical data feature of performance monitor -- this takes a long time if you want to run through a week of data. I looked through the built=in reports and they try to graph things and do all sorts of fancy stuff which I do not need.
What to do? Write my own report!
The only caveat to this is you can only use uncompressed data. I spoke with support about this and there is no way to uncompress the data or at least not one that was easy (or that they would share) so I increased the amount of uncompressed data on hand to one month.
Attached are two report definitions; one for a single server and another to run against a collection.
I hope you find them as useful as I have.