The majority of climbers live their lives without ever using a slipper. These are, it's fair to say, a specialist product when compared to the more general purpose adaptability of a lace-up or velcro rock shoe. Part of the reason for this is that having laces, or velcro straps, makes a shoe much more adjustable, so if the fit isn't quite right then you have some leeway. With slippers there's none of that, so the fit needs to be right straight off, because there's no place to hide if it isn't; however, when it's right there really is nothing quite like it, because slippers really are amazing. And the Instinct S is a particularly good example.
It's worth mentioning before we go too much further than I was a big fan of the previous version of this shoe - the Instinct SR. Back when I reviewed the original I said:
"Whilst I enjoyed using the SR, the big question is would it replace either the VS or VSR in my bag? A single word answer is difficult, because whilst I think it's unlikely to replace either of them for me, I would add it in alongside them (such is the modern age, where someone cannot leave the house without at least three pairs of shoes in their pack)."
Interestingly, as time went by, I found myself - more often than not - just packing the Instinct SR, particularly whilst bouldering or low to mid grade trad climbing, because they were not only a supremely comfortable shoe, but also gave me a good level of performance and sensitivity. This has only been enhanced by the development of the Instinct S, which is a massive step up in terms of both performance and sensitivity, whilst also retaining the comfort that made its predecessor such a joy to climb in.
It's impossible to write this review without referencing the Instinct VS and VSR, which have to be two of the most popular performance shoes on the market. There are many reasons for this, but one is that they're fantastic all-rounders. The Instinct S is similarly versatile, capable of performing on a wide variety of different rock types and disciplines, both indoors and out. Where they differ is in the levels of sensitivity and power they offer, both of which feel like a step-up from the Instinct VS and VSR, partly as a result of its unique tensioning system, which runs the whole length of the shoe, from above and around the toe right the way through to the heel.
At the time I really liked their predecessors, but they now feel quite clunky, cumbersome, and a little basic in comparison, which makes the fact that the new version is actually heavier seem quite surprising (490g vs. 450g per pair, size UK 7 / EU 41). Whilst the fact it's a slipper undoubtedly make the Instinct S a more specialist product, it feels like it has more of a unique selling point than its antecedents, as it's just got that little more oomph. Plus, it looks unbelievably cool.
Historically the weakest point of a slipper would be the heel, because without a strap or lace to hold your foot back within the shoe, there's a chance it'll slip out. It's a sub-optimal state of affairs when, mid-heel-hook on a project, you feel your foot coming out of the shoe, because that's your attempt over. Whilst a large part of whether or not the Instinct S's heel works for you comes down to the shape of your foot, the fact it's quite narrow, and is further bolstered by the shoe's tensioning, means that it's a good a heel as I've ever had on a slipper. The M50 rubber on the side panels is super sticky too and the slight lip at the back can be used to great effect on more marginal edges and rugosities.
Over the last few months I've used them trad climbing, sport climbing, bouldering, and indoors, and have been massively impressed with how they've performed across all disciplines. Whilst they're naturally at home on rock types like gritstone and sandstone as a result of their sensitivity, they have enough power through the toe to perform equally well on more edgy rock types too (i.e. limestone, rhyolite etc...). I was particularly surprised at how good they were for limestone sport climbing, which isn't something I'd anticipated, but the balance they provide between sensitivity and support is pretty remarkable, and makes them a pleasure to climb in. For much the same reason, they also make an excellent shoe for trad climbing and soloing on the gritstone, or bouldering around a circuit somewhere like Font, because they offer a good blend of comfort and performance.
In short: they're really good at a wide range of things, but (as per the intro) it all revoles around whether or not they fit. We'll come onto that next.
The Instinct S uses Scarpa's FJ last, which differs slightly (but not significantly) from the FV last used in the Instinct VS and VSR. Overall I'd say that if those two shoes fit you, so too will the Instinct S. Size-wise I'm exactly the same in all three models, so you shouldn't have to change sizes either (which makes things nice and easy).
If you haven't tried on any of these shoes before then (to recap) the Instinct S, and Instinct range as a whole, sit at the wider end of the spectrum within the forefoot, but the narrower end of the spectrum around the heel. They feature a relatively central toe, so aren't radically asymmetrical, and are slightly downturned. It's quite a forgiving last, which fits a wide range of feet, and they don't have to be worn obscenely tight to perform well (snug yes, painful no).
In terms of stretch, I'd say they give a little, but not a lot, and certaily don't bag out like some slippers do (to the point they're barely worth using in some cases). The way I look at it is that they get progressively more comfortable and supple, rather than sloppy.
One of the most noticable areas of development with the Instinct S is around the toe, with its M50 rubber toe patch, and offset randing. The toe patch features Scarpa's own super sticky, super soft M50 compound, which - from previous experience - is the absolute business for toe hooking. Because it's nice and soft, and because Scarpa have integrated so many holes into its design, it's also extremely comfortable and flexible, making the Instinct S a much more adaptable shoe than the VS and VSR. Looking a little closer at the toe, Scarpa have used an ilga rubber (aka. rand rubber) around the toe and instep, which helps to provide the shoe with its stiffness on small edges, but they have removed this from the outstep, which allows you to spill out a little bit over smears and smedges.
Beneath all of this there's a 1mm Flexan insole, which is what (amongst many other factors) gives the shoe its stiffness, and a 3/4 length Vibram XS Grip 2 sole. XS Grip 2 really is the industry standard as far as stickiness is concerend these days, and as a result it's hard to find fault. Scarpa have opted to use 3.5mm, which is perhaps a little thicker than I might have expected (part of me was wondering if they'd go a little thinner than the VS and VSR, but it's exactly the same); however, with all the other features, and the way they affect the shoe's performance, it feels like a very different shoe. This goes to show how the thickness of the rubber on the sole isn't the be-all and end-all to how a shoe performs.
If you'd asked me whether or not I'd have recommended the old Instinct SR over the Instinct VS and VSR, my answer would realistically have been no, because the VS and VSR are actually a much better choice for the majority of climbers. But with the new Instinct S that choice isn't quite so simple, because with this slipper Scarpa have managed to up the ante in terms of both performance and sensitivity, which is quite an achievement. Whilst slippers are undoubtedly a more specialist offering, I would simply say try them on, because once they're on your feet (if they fit) you may find it hard to take them off (metaphorically, not literally…).