La Sportiva Blizzard GTX

I’ve only run in these shoes three times so far but one of those was a 67km leg of the Spine Race, on frozen ground, hard ice and snow - so I have reasonable experience of how they perform for their intended use.
Overall, they provide a very good balance of grip, cushion/protection and comfort, without excelling in any area.
For grip on ice, I found it to be noticeably poorer than Inov-8 Orocs that I’ve used previously. I don’t believe this is due to too few studs (as many reviews suggest) but because the studs are not very prominent. Running on flat or downhill ice was ok, uphill (especially if walking) led to frequent slips but no falls. However, I found them superior to Yaktrax on ice and much better than non-studded shoes. Grip on hard frozen mud, grass, snow and rock is excellent, as is grip in deep mud (within the limitations of a stiff shoe compared to a fell shoe). Your foot is also well protected from the studs, I couldn’t feel any pressure like I do in Orocs.
Fit is slightly more generous in the toe box and midfoot than the Mutant and the laces lock the upper well. The “one-pull” lacing means variable tension across the foot isn’t really possible. However the tongue/upper provides good protection from the laces.
The heel cup is rigid and unforgiving and was the reason why I switched back to other shoes after 67km of running. I was beginning to get pressure blisters on my heel edges. So I’d recommend being very mindful of the heel fit, especially if you have hard skin on your heels because the rigidity means it’s unlikely to get better with use/break-in. It was fine up to 25km but started to hurt after that. It was probably exacerbated by the hard frozen rutted ground and would have been fine on softer ground (e.g. snow) for much longer.
The back of the heel cup is also largely unpadded (similar to the Mutant) but I had no problems here, it is well shaped and didn’t irritate my achilles.
I can’t comment directly on waterproofness but have no concerns based on experience with other Sportiva Gore Tex shoes. There are no signs of wear after 85km (as you’d expect) and based on material similarities to the Mutant, I’d expect these to easily last more than 1000km.
Overall, highly recommended as a comfortable winter running shoe, as long as they fit well (especially in the heel) and you recognise their limitations on harder, steeper ice (where microspikes will still be needed).