Thank you for reporting this bug. We will make it our priority to review this report.
[FIXED-388] TabPanel doesn't accept animation
I'm new to Sencha, so I may be wrong about this, but it looks like the slide animation is hard coded in Ext.TabPanel.
A fix seems to be on Line 18933 (of ext-touch-debug.js beta 0.96)
type : this.animation,
Sencha - GXT Dev Team
Thanks for the bug report. The team is reviewing your suggestion and they will let you know what they decide.
Thanks, this has been fixed.
Twitter - @evantrimboli
Don't be afraid of the source code!