I really like the Arcteryx stuff and was lucky enough to get an Alpha SV at an amazing price two years ago. I wouldn't have likely paid full retail for it before, but owning some of the stuff makes me think I'd buy it if I really wanted it as it really is worth it. That said, I talked to a fella at MEC and he hinted that much of their product was designed by some former Arcteryx employees and they used the same plant to make quite a bit of their stuff. I'm not sure it's true, but some of MEC's stuff sure does "look" similar. And as I had said before, you can't beat MEC price-point wise.
Off the topic a bit. Two years ago, I bought a pair of double boots from MEC and used them for a couple day climb(winter) and found they were just a bit too tight. MEC took them back after taking 5% off the price I paid for them, no questions asked. I find them to be very solid to deal with:thumbup: .