What are some decent alt-tab replacements for Gnome?

I think these problems bother me with the native alt-tab app: - It feels a bit sluggish - it takes about 0.3 seconds for the alt-tab window to appear. - I'd like to configure Alt-Shift-Tab to go one window backwards (not sure who to do this with the native one). - I don't like how the **only** visible window is the window I'm switching too - I'd like a behavior similar to Windows' alt-tab.