Did you ever notice a battery life decrease using those? I know there are threads on the subject but I mean specifically the SGSII
Not sure I've had it long enough to say. But I just posted in the battery thread that I'm at 14 hours with 34% left in the tank. Of course it will hurt, but I'm a moderate user and I'm not playing beat-the-clock to get the phone on the charger each night so it works well for me.
That being said, some live wallpapers are hogs! You can usually tell because they will bring the performance of the app drawer or launcher down. Example, the 3d app drawer on the g2x is usually smooth as butter, super high framerate. When you get a LW hog, scrolling through the drawer becomes jagged, it loses that fluidity to it. This is usually how I tell if a LW is going to be a no go. Grass seems to be very light weight as far as LW go.