You can get Documents to Go for the Android devices. Free version will let you look at Word and Excel documents and the paid will let you edit/create documents as well. I think they also allow for powerpoint documents somewhere in there.
I purchased the Documents-to-go and have no trouble viewing doc, docx, xls, xlsx and pdf files. I have not tried to create or edit a document. You can also view power point but I have not tried that yet. My main purpose was to view documents and Docs-to-go does a fine job at that. The time it takes to render the document is acceptable. Documents are rendered locally - some applications use a remote server to render the documents and then display the result on the phone - I did not want anything to do with that kind operation.