Try GNOME3 (with Fallback mode)
GNOME3 is knocking on the door and is one of the most anticipated releases, we’ve ever had. If you already took the chance and tried out a Fedora 15 nightly desktop compose, you have seen the changes and improvements that have been made in comparison to previous GNOME versions.
On a modern graphic card, GNOME3 will start the GNOME Shell which is a complete break with the commonly known desktop environments. It has not task bar for task switching, instead it relies on Alt+Tab a lot. But don’t be afraid, you can still switch back to a so called Fallback mode if you prefer the old GNOME layout and behavior. Fallback mode will also be automatically activated on low-end graphic cards and so within virtualized environments. Just open System-Settings / System-Information / Graphics and activate Forced Fallback Mode if you got a powerful hardware but still prefer a classic layout.
Fallback mode is still not perfect yet (e.g. bright white handlers look a bit displaced) and has some bugs (e.g. application menu crashes after adding an icon from the menu to the panel), but overall it’s quite usable.
So wherever you are used to Alt+Tab and are interested in a new desktop experience, take a look at GNOME Shell. If you prefer a taskbar for window switching and menus for starting applications, just activate Fallback Mode.