I occasionally send a link of the Ext demo to a colleague when I want to to spread the word of Ext or show off a new feature. I recently did that and got a bit of feedback on a few bugs that were noticed... which is strange in that I frequently use the demos for reference and had never noticed them. They are indeed there so I thought I would point them out. Having a polished demo is a great advocate for the library.
Layouts/Feed Viewer - The Feed Viewer demo loads fine but the progress spinner continues to move even after the feed has loaded.
Layouts/Nested Layouts - The icon images in the west panel have bad references/broken links.
Form and ComboBox/Combo Boxes - The displayed source for the Data Sources example doesn't match what is actually being used.
Form and ComboBox/Combo Boxes - In IE 6 only, there is a disconcerting screen flash when this demo page loads.
Debug Console/Ext Debug Console - Entire panel disappears after just clicking on a single item in the property sheet editor. Click on DOM Inspector. Expand the HTML node. Click on the tag. Click on the right cell of the InnerHTML property. Click on any other property. Screen will clear.
All of these bugs are visible and repeatable in both IE 6 and FF 2 except where noted.