One of the many OpenSource projects that surround Snort is a new one by JJ Cummings of Sourcefire, named "thepigdoktah".
This is a tool basically for parsing and generating some useful statistics out of the performance logs that Snort generates.
Analyzing for you, Mb/s successfully analyzed, dropped packets, packets per second, size of packets. There are a lot of metics and statistics in the perfmon preprocessor files that Snort generates, and thepigdoktah aims to expose those to the user.
Take a look at the project here.