Get statistics on how ReadyBoost is being used by Windows

The most comprehensive information might be obtained using the built-in Performance Counters (which are probably being accessed by 3rd party tools like RBMon).

Simply launch the Performance Monitor (accessible via Management in the Control Panel or simply by typing "Performance" in the search box in Start Menu, it should then be among the results) and add counters. You can select the whole category ReadyBoost Cache by selecting it and clicking Add or you can pick desired counters from within the category and add them to the list.

The most interesting stats might be the Bytes cached, Cache reads, Hit read bytes and Total read / write stats. Your mileage my vary.

There is a program, ReadyBoost Monitor, that give statistics on how much data is in the cache, how much it is compressed by and how much data has been read from or written to the cache. I used it for a short while some time ago and it fulfilled my needs.