Yes it works, in either builds 496 and 497. But, maybe you have recently checked the option "Draw OSD message to Overlay" in the Preferences/video tab so that you don't see the feed-back of your action on the display, as you used to.
With a Right-Click on the video window, BSplayer let you access directly to the properties of the filters it needs to render the movie. But if you want this to work, you have to register the filter at first (using regsvr32.exe).
If you can see dedynamic in the list, then it should react to Ctrl+Up/Dn and Shift+Up/Dn (or whatever key you may have assigned in the Preferences/Shortcuts tab). If you don't see the filter, then check that the option is enabled in the Preferences/Audio tab.
Check also that your shorcuts have not been assigned twice
.
You may want to register Dedynamic.ax using Regsvr32 so that you can use the sliders available in this filter properties.
Hope it helps