Right now I'm a big fan of Club Monaco. I stopped buying here for a while because everything was black or white or black and white. Imagine my surprise last summer when I tried to buy a plain black skirt (so of course I headed to CM, where else?!?), and they didn't have anything that matched that description.
I'm really liking blouse-y styles right now, so CM is a good place to look. It's also a great store as Greg F says for finding sale items. The staff is great about it and don't look at you like you're a super big cheap skate for shopping the sale, which is nice.
That having been said, the staff were super nice and friendly, and proactive about asking if I wanted help without being pushy.
Great service combined with a nice shopping experience and a preferred aesthetic, who can ask for more?