Arc'teryx Arrakis 50

Took this bad boy for it's first real test in ICELAND. 7 day expedition where I climbed, scrambled, and backpacked through lava fields, snow-capped volcanoes, and insane 1000 foot gorges and ravines.
This pack took everything the Icelandic weather threw at me including all the rain and snow a freak blizzard hit me outside of Jokulsarlon and wouldn't you know it, everything inside was boooooone dry!
Great fit, customizable, simple features, and truly bombproof for extreme weather. Expensive? Yes and I was more than hesitant on spending this much on a rucksack, but if you take care of it, you could easily get more than 10 years out of this pack. But more importantly, don't skimp on the items that could save your life--especially the one that's carrying all your gear (or expensive cameras haha).
Not much room for expansion so either be prepared to pack light or ramp up an upgrade to the 65. OH! And forget the bladder sleeve..unless your bladder is 30 ounces or less. I attempted to "force" a 100 liter camelbak and nearly tore the lining. Just leave it alone or slip a thin book in their...not worth the effort to take it in and out.
As for the 420D ACT material? WOW. I slid down a 15 foot, 30-ish grade declining rock wall very SLOWLY and CAREFULLY (max traction) when I lost the main trail on the decent from the Glymur waterfall and had no other route option. I swear that given the abrasive volcanic rock the pack would be shredded pretty good...it wasn't. Scratched up for sure! Dirty? Heck yes! But literally took no lasting damage despite what I put it through. I have never had a rucksack, nor could conceive of another one that could withstand this sort of abuse.
Save up and buy this pack. Just plan out for your space requirements because I now need the 65, this pack is truly for 1-2 days/night, and that's packing VERY light. Enjoy!

Let's put it this way: you invest a lot of money in something and it quickly shows whether you regret it or whether it's worth it. If it's worth it, or so you think, you give it another year or two (especially if you're talking about ski touring gear) and you re-think it. This pack takes a beating, year after year, and it's not a regretful purchase.
What the Arrakis 50 is: a ski touring legend. It's sweet for everything from trekking to grocery shopping to skiing, mild downpours in the summer to cold dry tours in the winter to sloppy wet spring tours when everyone's stopped skiing for at least a month. Throw this pack in the water (not for long though!), on the snow, in the mud, and your stuff is safe and sound. Its comfy and elegant. The zippers were placed by a genius. Everything is close at hand. The suspension is minimalist and plush at the same time. It carries your overnight load and then compresses and rolls down to small enough to be a day pack.
What it isn't: I've found that this pack lacks the volume for truly massive missions, or when you're the goat bringing all the beer to the hut. You'll run out of space. So you end up with stuff on the outside of the pack, which is surprisingly easy to lash to despite its appearance. It can't do everything, and for big long hauls, size up.