Visit the site, and you can create a text document or spreadsheet depending on your needs. Why not call it Google Office? Google told me they felt that name already had obvious connotations of another product out there [IE, Microsoft Office], and they wanted to underscore that this was a different creature.
Google also explained to me that these products aren't likely to match many of the features that mature software-based word processors or spreadsheets have. This came up when I noted in playing with Google Spreadsheets that sorting was too rudimentary for me. Perhaps that will change, but the main point is that these online tools are not meant as or expected to wholescale replace existing products. That doesn't mean they aren't useful. Those with less intensive needs will likely find them helpful, especially if you have to share and interact with others.
How about that name? A bit clunky? Google said they were happy with it being descriptive and that no one would have any misconceptions about what's offered.
Love the name Writely? Wish it well. That name is now retired. Google Spreadsheets also sort of goes away, graduating from Google Labs and losing its standalone identity as it becomes part of the new service.
Want some reviews? Techmeme recaps plenty of people talking about them out there.