ExtJs 4.1 really breaks on every little tiny error. It took me two days to get my loginscreen running.
Now I see some things working but there are still problems.
For example. Somewhere in my code the hide() function of a button is called before the button is renedered (was possible in Ext js 4.0) then you got the most strange results like splitters not working, menu's broken. Things not related to the button.hide() error.
To get things working you must set firebug on break on every error, follow try catch and just fix every first error you encounter even if you think it isn't an important notification.
Even setting a width on a center region is a complete blow-up.
The use of Chrome developmenttools is useless in this proces, because you can not set that tool that strict as firebug.
The "upgrade/porting" process is fairly painful. That being said, if you ever get it to run again, performance is better on the older browsers. Our main screen went from 8-9 seconds load time on IE8 down to about 3 seconds. We had seen 4.0.7 load times down in the 6 seconds range but that was quite difficult to accomplish. The start up process had to be carefully managed/tweaked to make sure that rendering and layout happened as late as possible. Small code changes would cause rendering to happen early and then multiple layouts later the screen would finally show up. With 4.1b1 the sensitivity is gone. This performance level appears faster than the 4.1alpha release for our code base. Much of this I believe is attributed to the changes in the field layouts. Although I was somewhat dubious of the switch to tables from divs we were able to eliminate a significant amount of code in layout.component.field.text's sizeBodyContents routine.
The only issue we are seeing is extreme slowness in the setFieldLabel routine (300ms per label x 50+ labels). It seems that the doComponentLayout in that routine is not playing nice. We have worked around that issue for now but will go back and look at it at some point.
Same here, I eventually gave up with attempting to get a large app working with 4.1 there were just too many changes required. Layouts were way off, windows appeared blank and non-functional, etc, etc. It is very time consuming to fix these issues, and it takes time away from productive development.
I think the Sencha team should have some examples of large applications at hand. In the development process the small things were working. But if I migrate from version x to y.... with my application (wich is big), I can see in one glance that there are bugs. The Sencha development team should have better test applications at hand.
But changing from 4.07 to 4.1Beta doesn't require much changes. Only finding the bugs was consuming time.
If the posted bugs are solved for the Beta 2, I think version Extjs4 is nearly there. And indeed the performance of 3.4 is still slightly better than 4.1. But 4.1 could be more stable if the latest bugs are fixed.