There is no way to create or edit a richly formatted document, spreadsheet, or presentation online in OLW, the way you can in Google Apps. Instead, you must create those documents on a PC in a full-fledged Office application, and then upload them to your OLW area. Although it's possible to view the content of these files directly within OLW, the viewers don't provide enough fidelity for a client presentation, for example. You'd again need a PC with the full Office suite installed, or at least the Office document viewers.
OLW lets you store some non-Office documents such as PDF or text files, and you can view those files online as well. Sometimes the whole process with stored files gets a bit silly. For example, you can upload a simple unformatted text file such as README.TXT, but the only way to edit it online is to view it in read-only form, copy the entire text, and paste it into a Note.
If you've already got Office installed on all your PCs, OLW makes it easier to share files among them. But there already are plenty of other sites that let you store and share files on the Internet, such as XDrive. OLW takes a slightly more Office-centric approach by providing a toolbar in Office applications to make it easier to open or save OLW files. This doesn't seem any better than mapping a drive, and in some ways is more restrictive since it provides easier access only for Office apps.
Who knows, maybe I missed something profound in OLW. There's no doubt that it's a useful service for die-hard Office users, but it doesn't offer the same level of online document editing and collaboration that you find in Google Apps. Don't take my word for it, though. Go to the Office Live Workspace site, try it yourself, and form your own opinion.