When I heard that Supergirl was going to be introduced in this new season, I couldn't see the reason for adding another hot chick to the cast. They have enough problems figuring out what to do with all the other girls (just don't get me started on their misuse of Lois Lane) why introduce one more and screw her storyline up? This is not a good idea.
But that was then.
Now, after three episodes, Kara has kinda grown on me, in fact, I'm pretty much crushing on her. :p
But she is creating new conflict for the other characters, making the stories a bit more engaging. Clark has to convince her to control her powers, she has a thing for Chloe's boyfriend (and Chloe's boyfriend has a thing for her), her first ever encounter with Lois (unbenounced (sp?) to Lois) was to push her into the mud, and while Lana doesn't seem to mind her, Lex has got the hots for her like any red-blooded American boy would.
If they can get by that smarmy jerk of an new editor at the Daily Planet, this could be a pretty good season of Smallville.