It seems Google has slipped in some improvement for document viewing via iPhone and iPad (and Android). For quite a while, the only documents that really played nice (at least for me), were spreadsheets. You can now go to docs.google.com on your Android or iOS device and view formats such as .xls, .pdf, .ppt, .doc, and .docx. I didn't see anything about .pptx though, I guess we'll have to wait and see on that one. If they're supporting .docx, not supporting the newer Powerpoint format doesn't really make sense to me.
The only glitch I seemed to find is that Word documents aren't that pretty. Some of my old accounting Word attachments were formatted pretty bad. I checked them on the computer and it wasn't the actual document. That may be something that needs a tweak on Google's end.
Here's a quick tip for iPhone users as well. What I actually do is open the Google Mobile App and click Google Docs, it'll automatically route you to the docs.google.com page in Safari. So you can go that route as well.
Hit the jump for some screens!