The E can easily go down to B or A if you want.
If you follow the proper setup procedure, it's very stable. Set standard tuning, flip lever to lower tuning, tune it, flip lever back to standard, retune, flip, fine tune, flip, fine tune, etc. Flip up and down a couple times, make sure it's in tune, and you're golden. It'll eventually go out a bit, but for a set or gig you're fine as long as you flip up and down enough times to ensure the tuning is stable.
White lithium grease, graphite, etc, or any other dry lubricant is necessary to ensure easy, smooth changes. Same goes for the nut so nothing binds.
Anyway, they're great and they aren't heavy.