Well, some of us (admittedly a seeming minority) don't like her at all. I think she's more a 'popular' character rather than a 'likable' one. What we have seen of her personality has been hostile and arrogant at worst, working through cold and manipulative to cryptic and long-suffering at best. (Save for a single scene with Jillian, where she did display a sort of patronizing affection, though this may have been part of her act to keep Jillian under her thumb.)
I think what makes Wanda popular to most is not what is known about her, but what is unknown. How did she lose her tribe? Why does she follow Stanley? What are her ultimate goals and ambitions? Is there any kind of more human side behind the 'Dragon Lady' exterior? All these mysteries give people a lot to ponder, and allow them to 'fill in the blanks' right now with whatever they'd like Wanda to be, so she gets a lot of discussion time and is also quite popular.
And that's as close to Wanda apologism as you'll ever see me come. Personally, I jump for joy every time that manipulative, arrogant so-and-so suffers a setback (and get a second smile when I come to the boards and see the true Wanda apologists all flustered). However, in a way, that makes her a popular character with me, too, because it keeps me reading in the hopes of seeing her go down in flames. Yes, she's good character.
But I still hate her