I've been using Sencha Touch in a professional environment for some time now and I'm fully satisfied with it. The product is absolutely great.

I post today because it seems there is a bug in the 'before' methods of the animations('fade', 'slide', 'pop').
In my case, this methods are called whenever the user tabs between panels of a TabPanel component.

curZ = el.getStyle('z-index') == 'auto' ? 0 :el.getStyle('z-index')
This line exists for each of the 3 animations. It seems to get the current z-index of a panel, and adds 1 at the end.

I think the normal behavior would be to have an incremented z-index (0, 1, 2, 3...).
Instead of incremental, the z-index does the following : (0, 1, 11, 111...).

Which means that if I tab about 6 or 7 times in a row, the z-index starts to be very high and MessageBox (in my case) appears under the panels (because I believe it has a z-index of 10.000).

I could fix the problem by replacing the code above by the following.

curZ = el.getStyle('z-index') == 'auto' ? 0 : Math.round(el.getStyle('z-index'))
Hope I could be of some help.