As stated above, the notification light by itself is pretty negligible. If you have an app that turns on the screen when notifying you, however, that will drain your battery very quickly.
I put a shortcut to the manage apps. on my home screen, so after I'm done using something I go straight there, force stop the app. & clear cache. My battery lasts all day from 8am to about 10pm without needing to recharge.
I'm hearing impaired and am considering the Droid-X, having had a Blackberry Curve for a year. When I got the BB, the LED that tells me that I have an email or text message was hard to see in the daytime, so I got an app (BerryBuzz) that enabled me to make the LED flash white and brighter so I was better able to see it in the daytime.
Anyways, is the Droid X LED bright enough to be readily noticeable? I saw a brief demo at a VZW store but the guy didn't seem too knowledgeable about it.