Just adding in my 2 cents on this. 4.0.x was slow but using 4.1.1 in a couple apps and I don't see performance issues if you code correctly. For instance, I had a form that had 2 grids, fields of course, a tab panel. I replaced that form with the same form but when I removed I would suspend layout and resume after adding it. With Chrome I couldn't tell I did the removal and recreation. With IE I noticed a little flicker but it's not like I had to wait 5 seconds for the new form to appear.
Originally Posted by firstname.lastname@example.org
xtype : 'userdetailform'