hey,
I have the Lenz 4.0 -- I just got them early this season. the socks are thick. I have followed the instructions and so far so good. I have been wearing them nearly everyday because it's been really cold here in Vermont up until recently. I will wear them again today.
They were recommended to me by a friend who has had them for years and swears by them. I believe she got them in 2016-2017 and I saw it on her in 2019, she still uses them this season and she says they are going strong. The key is to use the interval for an entire day out. The app makes it easy to use so you don't have to fiddle with it to turn it on/off or change how much heat.
My sister bought me a gift certificate so I could apply it to the purchase and they were 15% off and I paid the rest. Yes they're not cheap, but I think many others recommend Lenz as well.
I know Hottronics were a little iffy back in 2019 or so, but have since gotten a lot better. A lot of the instructors here have them for their boots and love them. There are some that have both the hottronics and the lenz. I'm seeing heated gloves as well.
@skinnyfootskis There's a reason that boot fitters size down, my bootfitter explained it to me they can make more room in a smaller boot, but if they put you in a larger boot there's almost nothing they can do for you. I wear a size 8 running shoe (size 7.5 regular shoe) and I'm in 23.5 mondo boots. I have a 24.5 alpine touring boot and he asked me if I do replace it, to get the 23.5. He has worked on both downhill and alpine touring boot (which was fitted to me 4 years ago by someone else) and my feet have never been happier. It sounds like you don't trust your bootfitter though. If he is charging for all the tweaks you keep going back for, I would not trust him. But if they fit you once and do not charge for each time you come in to get them adjusted -- then going back often is normal for a lot of people.