IMO panda's lenient inputs is a godsend when you are working with real-world, dirty data regularly. It's my favorite API I've ever worked with because it lets me focus on my high-level tasks and it takes care of the things I don't really care about like whether I am working with a list of dicts or a dict of lists or whatever.

But once you've done the cleaning/exploration, you should move any heavy computing to a high-performance library like numpy.