We've done that for a few years, but in practice rarely used it. I think part of the problem was that starting recording was a manual process, so it rarely got done until too late. This year I'm considering making it always log when the robot is enabled, however I'm also concerned about overloading the classmate, especially with all the data logging that the DS software is doing this year.
It plays back the data through the same dashboard interface. I think it might be more useful to create a separate interface that reads the data and plots graphs over time instead.
http://forums.usfirst.org/showthread.php?t=13533