This was the most awaited feature to hide tabs in App Drawer. And in the version of Go Launcher Ex 2.51 they have provided this feature.
You can hide tabs in App Drawer settings. App Drawer > Settings > Tab Row (Show/Hide tab row)
I am sure you will appreciate hiding tab bar. Let me tell here, if you are using an Android phone and have not used Go Launcher Ex. You missed a good home replacement thing.
You can download Go Launcher Ex free from Android market.