While I don't claim to agree with the logic behind it, here's the statement from Don upon which I based my conclusions:
The "performance baseline" we have right now is 4.1 PR1. So it is a blocker to regress from there. This is currently based on measuring the Themes example and a few others.
Would be interested to know if 2.3 runs under IE 9 also.
Had a quick look at the online 2.3 examples under IE8 and it seems nice and fast. Will have to benchmark and see if 2.3 if the best route for my app.
Many thanks for that
Apologies as I seem to have taken this thread OT. However, i'll answer the questions raised ...
2.3 works perfectly in all IEs if you send the right doctype or meta tag.
IE <= 8 send <meta http-equiv="X-UA-Compatible" content="IE=7" />
IE > 8 send <!DOCTYPE html>
In fact, IE9 rendering was comprable to Firefox in terms of speed.
For example, a screen in one of our apps (200 widgets approx incl. grids, tabpanels, form elements etc) ...
There's also a few tweaks you can apply to Ext.lib.Event (which may not be in the official release; listener cache as an object vs array, _getCacheIndex, add/removeListener etc) which speed things up enormously, prevent memory blowout in long running enterprise apps and reduce the likelihood of the "Stop running this script" warning one typically receives on big destroys.
It will be a big problem for Sencha if the developers decide to switch to the very all 2.3 version.
This just show how wrong was the decision of releasing Ext 4.0 just to be on schedule, with the framework completely unstable.
I hope you Sencha guys learn from this mistake.
Ext is terrific!!