My Carv package showed up today.
First impressions of the quality of the components is very good - it seems well made and feels like it could be pretty durable. I test fit one of the footbeds and have my ski boots on (one with Carv, one without) and I can definitely feel a small difference in fit, but it doesn't seem like it will bother me at all and while I hadn't noticed it skiing last season, maybe there was a small amount of volume above my instep and the top of my foot that I could stand to have taken up, so maybe the Carv is a positive for boot fit for me.
The battery unit attaching to my booster strap is a pretty tight fit. There's not a ton of room between the buckle and where the strap attaches to my boot, so the battery only has a quarter inch or so on either side of it, but I guess that's all it needs.
I do have a question for existing Carv users though. What do you use to secure the section of the cable that protrudes from the boot when you're not using it? While I'm hoping I'll get to use Carv reasonably frequently, I won't want to use it every day, particularly if I'm mostly going to be skiing off piste. There's a pretty good length of cable sticking out of my boot with a somewhat fragile looking connector on the end of it which seems like it should be secured somehow to avoid flopping around and getting damaged. Maybe just tucking it under my booster strap or under my gaiter will be OK, but I'm not really sure at this point.