Upgrading from v3 questions

[brookd]

I have a large extjs app that in hope to launch this summer. I've been working on it for over two years!!

It's built on extjs 3.0 and I am considering if I will be able to move to 4.0 before the release.if any one has any insights please let me know:

• How backwards compatible is 4.0?

• Will live grid work with 4.0?

• Is there a significant memory usage and performance benefit in upgrading to 4.0? As it is now memory usage and performance (especially in IE) are Two of my biggest concerns

• I'm usinge high charts and the high charts adapter for charting. Looks like I could replace this with the new charts in 4.0. That would be good as the high charts library is pretty big and anywhere I can save a few kb would be welcome.

[tryanDLS]

There are several threads already started to discuss this. Please refer to those, and also the blog posts which introduce 4.0, as they also discuss where improvements are being made. There is also this thread http://www.sencha.com/forum/showthre...to-4-Migration which was started specifically to talk about migration issues.