Arc'teryx is very innovative and their products are well made, beautifully designed, and contain top-shelf materials. I live 10 minutes from their HQ and check-out their discounted gear frequently. Generally, I purchase either Arc'teryx or Patagonia. From my experiences, Arc'teryx makes the best Gore-Tex shell on the planet - I've tried a bunch of different brands. I also like their AC2 waterproof packs. They're heavy, but where I live waterproofness and extreme durability are paramount. Patagonia makes better base layers.
Great, innovative design and excellent materials. Fit is generally athletic and the cut is usually unsurpassed in the industry, feels like a tailored piece. Warranty is pretty good, though not as easy as Patagonia. Performance is excellent.
While innovative, sometimes I think their gear is over designed and is therefore lacking or over-engineered. It's also bleeding-edge tech - sometimes. For example, I have a dually belay parka, which is a $550 [+ 12% tax here in Canada] jacket. It's a great piece, but the hood doesn't have any volume controls. So, it's fine with a helmet on, but when you're sitting around camp, you look like the grim reaper and it interferes with your headlamp and visibility. None of their soft shells and non-goretex insulated jackets have this control. Even Patagonia's minimalist Houdini jacket has a hood volume control. This is something I would expect in a $600+ jacket. I've owned two AC2 packs and while I love them, both have suffered from failures/breakage with the laminated parts. I just had a softshell replaced b/c all the laminated seams started to blow-out. Of course the prices are ridiculous. $300 for a pair of gloves! Seriously? They're nice gloves, but the next best thing in the marketplace is much warmer and 1/2 the price. A big chunk of Arc'teryx gear is made in China now and the prices don't reflect this. The more complicated items are made in Canada, but I'm sure this is changing.
So, in a nutshell, I wouldn't buy Arc'teryx b/c it's Arc'teryx. I'd only buy it if it's going to meet your needs better. I never pay MSRP for their stuff, I only buy at the factory sales.