Animated sliding tab bar

This is a sliding tab bar I did for a recent client, I know that the tab bar droped behind in popularity for the sliding menus lately but I still get clients asking for them.

The problem that I have with tab bars is that they are limited to 4-5 tabs and eat up a lot of screen size, with this approach I tried to solve the seccond problem.

View full size animation: http://dribbble.com/shots/976474-Sliding-tab-bar/attachments/112930