WordPress for a CMS is fine. WordPress for everything SharePoint can do? Not even close. Frankly, SharePoint's got a lot going for it (though 'ease of use' is not on my list). It's insanely complicated and robust and, for a lot of Big FatCat companies, this is why it gets used:

SharePoint is a bit of a big beast and part of the reason it goes well is that it integrates quite well across a number of feature sets.

That's exactly why we use it here. We don't need comments or spam filters. We DO need to be able to integrate documents with webpages with private areas and LDAP and everything else Windows we have here. So yeah, totally makes sense.

Not that I don't agitate for WordPress for some PARTS of our site, but even with my 'WordPress for everything!' jaded POV, I can easily look at my company and go "Oh yeah, WP's not the one for us right here."

(I work for a very large, international bank, if that helps)