Having spent a little bit time with all of them now, I haven't noticed a single new feature that actually makes usability better. So far it just seems like features have been dumbed down or (more commonly) removed altogether. Has anyone ever used iWork on a tablet? Like honestly? I used it as a gimmick a few times, but I have no idea why Apple would think this is the way to go with iWork development.
Also Numbers is still a terrible program, missing many core features of Excel. It's good for like, making your family budget, but useless for anything else. I imagine the new Numbers also still has the 65'554 row limit and 256 column limit that crippled Excel prior to 2008 (and Prism prior to v6), although I haven't checked.
Pages is an acceptable Word replacement, but if you save in .pages formats, it basically means you can't collaborate with anyone else on a document you're writing. Also, EndNote is supported in Pages '09 (and probably even older versions).
I love Keynote but the new version removes basically all of the functionalities that made it better than Powerpoint for me (namely: ability to retain original vector graphics in a saved .keynote document... also capability to make animations < 0.2 seconds long, don't know why PPT has such a long hardcoded limit).
E: Also warning, if you open an old document in iWork '13, it seems to convert your document to the new format, then overwrite your old version, then auto-save. So, copy anything important before opening it.