I use live wallpaper. I have a very nice on I paid a buck for and I find it enjoying to look at.
It doesn't slow down my Droid or for that matter really suck up more battery. Most of the time it's not even up.
But how important is it? On a scale of 1 to 10 it's about a 1.5. Maybe.
I put them on before going into a meeting when I know there will be iphone fanbois in.....And leave the screen on with the X laying on the table.....Looks are priceless
I kept one on for about 30 sec and then went back to my regular wallpaper. They look nice but don't really do anything for me.
I think the longest one for like a couple of days was the livewallpaper that changed with the weather forecast but that is about it.