Had these for about half a season - wanted to put them through some use before writing a review.
First off, yes they're crazy pricey (unless you get them on sale). However, a perfect pair of gloves are worth their weight in gold, especially if most snow gloves don't fit stubby fingers (like mine) well (I wear a cadet medium golf glove if that helps), and I've been looking (and settling) for quite a while.
Sizing, they are shorter than average in the finger length, which works great for me. However, the rough edges of the stitching on the inner glove can dig in to the webbing between your fingers if they're a tad small for you. Also the fingers of the shell are pretty wide in diameter, though I suppose that may have something to do with articulation and/or warmth.
Durability wise, they've held up fine. The leather color seems to have faded slightly (not really a big deal IMO - probably from the Spring sun), and the shell material shows no wear after deflecting a few branches at head level. The leather is _very_ supple, and I was a bit cautious about not holding my skis by the edges too firmly, but I haven't had any cuts in them so far.
Design - Sounds like I'm in the minority in liking that there's no idiot strap/leash, since I never used them on any of my previous gloves (I did a bit initially, but they just got annoying). Stays in line with Arc's minimalist design philosophy. The wrist cinch works, but could use a little bit more development - the strap's excess slack can flap around a bit when you're at speed - fairly minor though. The one-handed cinch and release at the cuff work wonderfully. The stiff cuff of the inner glove makes it easier to don the glove (never liked the fidgety cuff to cuff velcro solution of other gloves with removable liners). One thing that would be a nice improvement would be including something to hook the gloves together when you're not wearing them (like the little plastic clips every other glove has). I used a small carabiner on my pack through the cinch loops on the gloves as a fix, but a plastic thing only weighs a gram or two (and could be easily removed by the hardcore minimalists).
Dexterity and warmth - They are indeed very dextrous, though I do have trouble literally picking up a dime from a flat surface with them. Though with just the shell (and optionally a thin liner), yup - able to pick up a dime off my desk. I didn't find them super toasty in the mid-high teens (Fahrenheit), but it could've been due to other factors - will need to see next season. You do need to cinch down the cuffs well to maintain warmth, otherwise the warm air goes right out the back of the gloves. Windproofness worked well too - no gaps of cold felt when it was gusting at the peaks.