Rooting the Nook essentially enables to install some apps from Google Playstore that are not available from BN app store; it also enables you to customize the Nook's user-interface more like with typical android tablets.
Rooting does not alter the release version of the base Android OS used by the NC, which is 2.x and quite dated by now (see
http://en.wikipedia.org/wiki/Android_version_history), hence there is a good chance that many recent or new apps from the Google Playstore would not be backward compatible to run on it.
If you want experience a full Android experience on your NC, consider running a custom ROM such as CyanogenMod off an SD card (hence leaving your NC internal stock ROM intact), see
http://forum.xda-developers.com/show....php?t=1941858 for some how-to info/pointers.