Which part of it?
I have been a power user of MS Office since the days of Windows 3.1, and I have been using Word even when it was a text-based application (and, BTW, the best text processor available then).
At the moment I have both iWork and MS Office 2011 in my Mac and Office 2010 running on Win7 on my desktop. So, I have the opportunity to compare the two. And here is what I've found:
Word vs. Pages:
- If you want to create a long document with a lot of cross-references and illustrations (book, academic thesis, instruction manual), go look somewhere else. Word has still the tendency of corrupting the files once they get complicated enough. Pages does not really offer the necessary facilities for such work.
- If you want to write a quick business document, both will do. Word is better in terms of universal compatibility, as most of the people still send .docx's around (most of the time the reason is beyond my comprehension).
- If you want to make something good-looking, you are faster and better done with Pages. While Pages is not exactly a DTP program, it has some quite nice features to that direction.
I use both, and I need both.
Excel vs. Numbers
Excel blows Numbers out of water. Unfortunately the rate of development of Excel has been extremely slow, it has most of the deficiences it had in the 97 version (limitations in two-dimensional graphs, only a small number of points allowed in a graph, bad interpretation of date data, etc.) Numbers is fine for making a quick good-looking pie or bar diagram, but not much more.
Keynote vs. PowerPoint
Keynote is better for making good-looking presentations. PowerPoint is engineerish in some ways, and while the difference between the two is not that big, Keynote is better. A lot of things I do with my Keynote are not doable in PowerPoint. On the other hand, there are some things which PP can do (such as 3D arrows and boxes) better than Keynote, but still I find Keynote a better companion on the road (especially with iPad as a remote control).
So, I find it difficult to call iWorks a joke. I use both, and if Numbers got up to speed with Excel, I'd happily abandon Office.
However... On the tablet format... Serious work? No. And this has nothing to do with operating systems or companies. Keyboard is a superior way of inputting large amounts of text, and a 10" display is ridiculously small for many tasks.