Each to their own. I never found her particularly enthralling.
Well, personally it didn't matter if it was her or someone else... I just felt like too much time was spent on the talking animals, and not enough was spent on the Tarzan Legend. Plus, they totally massacred the book. Not surprising, since Disney always does thier own thing. But Tarzan is a well established character in our pop culture. We've parodied him (George of the Jungle), the Japanese have parodied him (Parzan in Dr. Slump), and even Disney did it before (Ducktales episode- "Jungle Duck" which ironically stuck closer to the book than the film did).
They should have called it the "Turk the Monkey Movie."
Of course, it doesn't help that Rosie isn't as endearing as Robin Williams, Nathan Lane, or even Danny DeVito.
Personally, I think Chicken Little was a cute film. I dug it. it wasn't half as good as something Pixar did, I found it pretty endearing. I agree it could have been better had the big wigs (but not the small wigs) messed about with it. And it did need more Don Knotts. But still, better than half the stuff Dreamworks pooped out lately.