Currently if you drag the tabstrip past the "endpoint" it shows the drag, then rubber-band-bounces back when you release.

I think the current effect is pretty nice. 

Do you have a specific suggestion on this?

My thinking here is that we might want to limit the x-distance you can continue to drag once the endpoint is reached (say, only an additional ~20px). Right now you can continue to drag the tabstrip indefinitely. But I'd say this is low-priority and I would be ok if this were made a WontFix.