In reply to Pete_Frost:
Thanks for the post.
It used to be that years of experience was a good buttress against accidents, but that is no longer true because of the speed of evolution of gear. Experience can be worthless or worse than worthless when it comes to handling new gear, and experienced users can be overly complacent about the value of their no longer relevant knowledge. I've committed this sin and fortunately not hurt anyone else or myself as a consequence.
This seems especially true of belay devices. They aren't your grandma's Sticht plate, and have a learning curve that turns us all into noobs (and maybe also boobs) when we grab 'em at the store and head straight out to the crag.
I think lowering with guides plates, at least the ones I've seen, is dangerous. There is a very rapid transition between being locked to offering almost no resistance. If you don't know about this you'll drop someone for sure, but even if you do know about it there's a decent chance you'll cross the control threshold. Saying this doesn't happen if you do it properly is just proposing a definition of "properly," not confronting underlying flaw of the gear.
Knowing the devices are flawed, lowering ought to be done with a backup. This could be a prussik on the brake strand or a munter hitch on the harness or a hip belay, but something behind the plate to provide friction when the plate suddenly releases.