I've got 2 Vamos, one stays at home at my computer desk. The other is a backup to my MVP for when I'm out in places where it'll be used heavily. Mostly bars. Just about every weekend I'm playing with one of my bands in smoke filled bars. I leave a vamo, ready to use, in my gig bag in case my MVP's battery dies or craps out.
I got my first one about 6 weeks ago and not had a single problem.