If you like cooking Asian or buying your own fresh fish (and you'll smell it coming in), Mike's is the place for you!
I'm not much of a fish eater, but whenever I'm in Mike's, there is always a line of people at the back fish counter.
However, it's the Asian Market that grabs my attention - and my wallet - every time. Tofu here is in general $1.25 cheaper than any grocery store for the same brand. Miso is about $2 cheaper than Fresh Market. Soba noodles are roughly $1 cheaper than World Market. And then there's all the various ingredients and treats (like lychee or coffee-flavoured candy or duck eggs) that most grocery stores would never even think of stocking.
Can't recommend highly enough.