With this current release, you will be able to share whole spreadsheets (workbooks), but you won't be able to share individual worksheets. However, if you have already shared specific worksheets with others, it will continue to the work the same. We will bring this functionality back in a future update. We have also temporarily removed the notification email when a shared user modifies the spreadsheet.
とりあえずGoogle Spreadsheetsで凌ぎました。
2012/12/21 16:59:08ですが、タイトルとシート見出しが表示されるのが、チョット残念です。