iWorks for the iPad is a cut down version of iWorks for the Mac.
It is still a pretty capable set of programmes though. But you may be initially deceived by the rather simple appearance of the individual apps. Pages for example at first sight appears little more than a substitute for Notepad on a PC. It's only when you dig under it's skin that you discover it can do pretty much all the basic word processing tasks if not having every bell and whistle of Pages for the Mac or Word on a Windows PC.
Same applies to the other elements of iWorks.
My only gripe (at least with my iPad 1) is the real pain involved in anything other than just typing some text. Maybe it's just me but navigating round the screen, positioning the cursor to type new text in the middle of existing text and simple tasks like that are much more hassle on the iPad than the Macbook I have or any Windows laptop/PC I've used.
If you can get on with the user interface of the iPad then iWorks is not a bad set of apps to have. And I can confirm that they will open many Microsoft Office docs. Though some really complex documents can throw it. But most of what I have made in Word and Excel seems to open fine.
Although I don't use Powerpoint very much, if at all, myself I have seen colleagues at work transfer Powerpoint presentations to Keynote and have them work without too much hassle.