CoordinatesNOW!: Why is the "Get Last Known Location" option grey'ed out?

With the current released version, you must be on one of the Latitude/Longitude input screens (not the UTM screen) for that option to be available. Your "Location" icon in Android Settings must also be active, and you must also have recently gotten a good position for the app to be able to request it from the Google API on your device.

CoordinatesNOW!: Does the "Get Last Known Location" option get my current GPS position?

Unfortunately no. It gets the Last Known Position that the Google Location API has on your device. This may be a position you were at previously if you don't have a good GPS lock, not your current position. If you regularly turn off the Location function under Settings on your device, and only turn it on to get a position, you may want to bring up a GPS application first to assure you have a good lock, then request the position from "Coordinates NOW!". Good GPS apps I've tried are "GPS Test" from Chartcross Limited, and "GPS Essentials" from mictale.com (go to the satellite screen and wait for a good lock).