A friend of mine was interested in the vest liner and possibly an extra battery for it. I've thought about one as well to cut down on how many clothes I have to wear when I'm working outside and it's -10.
Quite a few guys ordered that, I might have to do the same for myself.
I have a battery powered vest liner at the moment and use it all the time.
I put it on over a t shirt to take the dog for a walk.
I bring it on camping trips with me and walk around camp with it on.
If it's below zero I sometimes keep it on in the sleeping bag for a while to warm it and myself up before going to bed.
My favorite use is when working on bikes in the garage or the driveway in cold temps. Wearing something bulky just gets in the way and restricts my movement too much. But a cheap thermal shirt and the vest over it and I am toasty.
Unless I'm putting goldwing tires on a concours, then there is no need because I work up a helluva sweat getting those things on by hand!
Try one, they're only $75, skip going out to dinner twice and it's paid for.