This LifeHack post list some Enhancement Requests for the Google Web Applications (Gmail, Google Reader, Gcal, Google doc & spreadsheet). At least for Gmail, the requests are relevant:

• Sorting should be available. Even if the google way to find something in Gmail is to use the search form.
• Two panes: It’s frustrating to loose the inbox view when opening an email. Yahoomail for instance open the mails in tabs.
• Dragging email in label could be nice
• Display message size
• Select multiple attachment
• Display a progress bar of upload