San, I don't know if I'm the best judge of quality. I have heard a few people from YLF complain about their quality, but I'm not sure why or what pieces they were referring to so I can't say for sure what the specific issues were. They stock many different brands, both their own "house" brands and others like Sweet Pea and Joe's Jeans, and I am drawn to some more than others. I can totally see you liking Leifsdottir (which is sold outside of Anthro). Among their store-specific brands, I really like Odille, Elevenses, Ett Twa, and Idra. I'm not such a big fan of Moth, which tends to make a lot of shabby knits.
The biggest complaint I hear about Anthro is that it is too expensive for such casual clothing, but I don't think that is a fair statement. If you wear casual clothing most of the time, and you have the money, why not spend more on it? You'll be living in it every day. For me, investing in a suit would be a tragic waste of money, but investing in a gorgeous artsy blouse and a great pair of jeans would be an investment. People have different needs and lifestyles. I think a lot of other stores already have "smart" and sophisticated clothes covered, so it's nice that Anthropologie filled a gap.
I don't have a lot of clothes from them because they are so expensive, but what I do have has held up significantly longer than most of my other cheaper clothes. The blazer I wore to the YLF convention was purchased in 2005 and still looks great and gets softer each time I wear it. Unfortunately it does not close over the bust so I can't wear it anymore, but I keep it around just in case my dream comes true and my bust shrinks someday. Four years probably doesn't seem like a lot to you, but it's like dog years for me
I don't know. I don't find them particularly better or worse than any other store. Their knits are overpriced for the quality, but so too are knits from BR, J Crew, Ann Taylor, and most other stores. As with all stores, but especially so for Anthrpologie, you're paying for the design. You can definitely find cheaper knits at the Gap or Old Navy, but they aren't going to have the quirks and subtle details of the ones you'll find at Anthro.