Evolution of the WordPress interface from 2003-2008
planetozh.com
planetozh.com
It feels to me as if it was built like a crappy powerpoint presentation: sliding and fading just for the sake of sliding and fading. Everyone thinks "Ooh, ahh!" but there really isn't any added usability to the effects.
In some parts of the interface, you have to click multiple times to get to something you shouldn't have to click on to see at all. Once again, you click just for a dropdown. Then you have to click again to get to where you want to go. Eye candy for the sake of eye candy.
In my opinion, the 2.5 Happy Cog design was the best of the bunch. It improved drastically, usability-wise, on top of the previous release, and it did so by re-aligning, no re-designing. You may argue that Happy Cog was limited by the fact that they had to base their work on a previous structure, but I really believe this is the best way to improve UI: incremental updates, each improving upon the last, instead of one quick release that wasn't too well thought out.
"Shiny" animations almost always make a user interface dramatically slower to use, as you have to wait for them to finish!