Although the previous answer was already accepted, there are a few points I'd like to clarify.
Ext does not use a "modified" GPL license. It is fully dual-licensed under the standard GPL v3 and the Sencha Commercial License. There are FLOSS exceptions to make it further compatible for plugin/extension developers, etc., but the GPL license is the standard license.
The list of Cons, while mostly fair points in general, is somewhat meaningless without some context. Comparing Ext JS to jQuery is also meaningless -- that's comparing apples to oranges. If you compare Ext JS to other comparable RIA frameworks (Dojo, YUI, Sproutcore), then things like footprint, CSS/HTML complexity, debugging, etc. become pretty even (or at least a more useful contrast can be made). Just saying that those things are "cons" in the abstract is not really accurate, since they are mostly just requirements of any complex RIA framework.
Regarding a few specific points, this list (according to the source article) references Ext 3.0. The current version as of this writing is 4.0.7. The total code footprint has actually increased since 3.0, but Ext now ships with a dynamic class system and build tools that allow you to create optimized builds based on your application's dependencies. So yes, it has a large total footprint, but no, you do not have to include everything.
CSS/HTML complexity is a given, based on the complexity of the widgets and the layout systems supported by Ext JS. This is very common in the world of RIAs and not comparable to simple jQuery plugins. Ext 4.0 now uses SASS/Compass btw, with generated CSS, so customizing the source styles is actually much easier now than in 3.0.
Debugging is also somewhat easier in 4.0 (again due to the new class system) but is certainly harder than any statically-typed language like Java (GWT). This is an issue for any JavaScript based frameworks, not just Ext.
It is certainly possible to bookmark pages in your app if you implement history/state support (both offered by Ext). This is something you must do since it is app-specific (there is some automatic state management at the individual widget level) but it's certainly possible. Again, this is a common RIA issue, not anything specific to Ext.
The list of Pros I would agree with (except point 5 which is presented out of context and makes no sense). In fact the documentation and help guides have gotten way, way better since version 3.0. If you want specific comparisons between Ext JS and other RIA frameworks, just search SO as that's been well covered before.
