I agree with Jason Fried from 37 Signals that it probably is enough for most people. Google doesn’t really need to put together an exhaustive office suite because most people don’t use all the applications found in Office Pro or even the scaled down versions. I use Word, Outlook and Excel everyday. But I don’t use Powerpoint very often and I haven’t used Access in years. I’m pretty sure I could be happy using about any other word processor. But I’m hesitant to use an Excel or Outlook competitor since I know my around those two products quite well.
The other question I hear asked about product like Writely is this: Can I save documents to my machine or is everything I create stored on someone elses servers? It’s one thing to have someone host my email but it’s another thing for them to be responsible for my spreadsheets full of financial data.