I just got back from two weeks of alpine climbing in the Bugaboos, and my hips are still sore from the 70 pound pack that I humped the 3000 vertical feet from the trailhead to Applebee camp and back.  We all know how much weight matters in the mountains; that's one of the reasons why I'm in love with my new superlight Salomon mountaineering footwear, the S-LAB X Alp Carbon GTX.

I pretty much lived in the X Alps for these last two weeks, and I was continually impressed with their comfort and performance - not to mention grateful for how wonderfully light they are at just under 18oz. 

Where I see room for improvement: 

• Most Salomon trail runners have a keeper pocket (garage) for or the Quicklace closure on top of the tongue; the X Alp does not have this feature, presumably because the gaitor makes it superfluous; that said, there were numerous occasions when I wore the boot with the gaitor unzipped and rolled over, and I would have appreciated a dedicated place to tuck in the Quicklace to avoid getting caught on rocks and branches.
  (**Update from previewing the new X Alp GTX 2: it features a Quicklace garage!)
• Another challenge with the Quicklace closure: I noticed it would work itself a bit lose after prolonged crampon use. Not a big deal because the zipped up gaitor still provided plenty of backup stability, but it's a noticeable performance difference to how the Quicklace closure works on trails. 
• Finish: after ~20 days of intense use, the boots are overall still in very good shape (including the soles, which I was happy to see are barely showing any abrasion) but the side seams of one of the tongues is beginning to dissolve. 

What I loved: 

• It's the lightest, most comfortable mountain boot I've worn. The inner low-top shoe feels as comfortable as the Speedcross (my favorite Salomon trailrunner), and the weight speaks for itself. 
• The X Alp GTX climbs like a pro. I covered a lot of 4th and easy 5th class terrain in these boots, and managed to get them to slip only once: on a wet lichen-covered slab. The Contagrip sole is excellent. 
• The boots are waterproof thanks to the built-in goretex mini gaitors. Coming back from long alpine routes late in the day, I was often slogging through wet snow and slush (add the occasional stream crossing, too).  Throughout all of it, my feet stayed dry and warm. 
• Good crampon compatibility. My Salewa Alunal semi-step crampons worked like a charm; I only had one of them come lose a single time over the course of two weeks. 
• The Quicklace easy-cinching closure is awesome - I know and love the system from many of Salomon's trail runners, and appreciate having it on the boots; no fiddling with laces while wearing gloves.

All in all, I was highly impressed with the X Alp Carbon GTX and am excited to have this boot in my quiver for three season mountaineering.  I wouldn't use the X Alp for super cold temperatures (like my upcoming return to Aconcagua this winter) or sustained steep ice as I would want more rigidity for that, but for three-season mountaineering through variable moderate terrain this boot is the ultimate footwear.  

***AUG 5 UPDATE: the S-LAB X Alp GTX 2 is coming!

I just had the opportunity to check out the new and improved 2017 X Alp GTX 2 at Outdoor Retailer. It now has a Quicklace garage! Other updates include a slightly asymmetrical zipper on the bootie to improve flexibility, a slightly larger tongue, and a new black & blue design rather than the old black & white.