Yes I had the GPS on. I always have it on. It doesn't drain the battery unless a program uses it.
This is false. If you have the GPS on it will be a huge drain on the battery.
And there is really no need to guess about these things. The Droid keeps track of what is using the battery power. Go to settings > about phone > battery usage.
One of the things you'll notice on the battery use chart - All those apps you see running in the task killer app that you think are eating up the battery? They aren't.