With stock unlock screen, the time displayed also contains the percentage charged when your phone is plugged in.
I may add this to the lock screen clock widget at some point, but for now as people have mentioned there are widgets that can do this.
I'd there anyway you could make this into a home replacement?
Hrm, so the Home Helper would actually launch WidgetLocker, then you could have double-tap for QD and single tap for WL (or vice versa with PowerStrip). This would have to be an advanced configuration as it could really confuse some people. I'll think about it.
Or even cooler, is it possible to make widget locker display your default homescreen as the lock screen? Instead of making a separate screen with widget locker?
Unfortunately this isn't really possible. WidgetLocker can't read the configuration from your home app and even if it could it can't add Widgets to itself without direction interaction from the user, so it wouldn't be able to automatically stay in sync anyway.