Having the text-entry field resizing was alone worth the ugprade to FF4 for me. Right now, I can grab the corner of the text entry box that I'm typing this into and resize it to any size I want. Very very useful.

I'm also happy that FF4 seems to be even faster and handles lots of freshly-opened tabs better.

I worked around all my other FF4 upgrade gripes and I'm quite happy with FF4. My upgrade gripes were:

- My Zoom Toolbar did not work in FF4. I have worked around this by replacing it with "Zoom Page 2.2", which I like even better.

- My favorite behavior from Tab Mix Plus, which was: Double click on a blank area of the tabbar to open a new tab, did not work in FF4. Because the tabs, even when moved down to their proper place, were still considered part of the titlebar, a doubleclick on the blank tabbar maximized the window instead of opening a new tab. I worked around this by turning on the old-school main menu feature in FF4, which acts as the dividing line between the tabbar and the titlebar, thus making all the old Tab Mix Plus features work exactly as before. I hated the lack of an old-school main menu anyway, and so that actually killed two birds with one stone.

Other than that, I haven't seen too much plugin incompatibility, but I don't use a gigantic amount of plugins anyway. I've pretty much got all the important plugins I had from the prior FF version, and I'm happy.