1. The menu bar at the top is now wasted space. 2. The task bar is on the side.
Shortcuts to spreadsheet, worth authoring, etc, should be hidden away in the menu. Honestly how many new spreadsheets do you create every day? Not many. What you might do is double-click on a spreadsheet and have it open, but that doesn't require a big shiny shortcut being in the taskbar.
These are just defaults and can be changed, but still, I feel as if they are poorly considered defaults.
The topbar in Unity contains the menu for the currently focused window (and, in the future, hopefully the currently focused application). This vertical space had to be used anyways - the clock and some sort of notification area are essentially mandatory.
As a person who primarily uses Mac OS X, I think that the menus are the best use for the vertical space that those items provide. I can use Cmd+tab or Exposé for switching applications, so a list of the currently open windows isn't particularly relevant. By moving the menubar to a single spot, if anything we save space.
That sidebar is truly awful though.