That's not necessarily accurate with that short movie. After all, it doesn't actually show the app starting up, it just shows the bouncing stopping. When you launch Adobe Acrobat for example, it stops bouncing after a few bounces but the splash window stays open with the startup status info (the "Initializing blah blah library" text) quickly flashing by and the app isn't actually running until 10 seconds later.
Apple revealed in a document somewhere that the Dock icon bounces until a Carbon app calls WaitNextEvent or RunApplicationEventLoop. Cocoa apps probably bounce until their event loop fires the first time (however that works).
Basically you can write code so that the initialization part of an app happens later (using timers or shared libraries loaded as needed) and get right into the main event loop thereby reducing apparent Dock icon bouncing.
By rearranging some code, not actually reworking anything except when things happen, I reduced launch time of an app by one full bounce. A little more serious work and I could get it to two total bounces (instead of the 4+ it takes now totally unchanged). This is on a G4/450 w/10.1.3.
This explains why some apps can appear to launch really fast (IE) and others (QuickTime Player/iTunes) take much longer. It also makes bounce counting nearly useless if an app is made to do more work initially, such as connect to a remote server causing the icon to bounce until the app finally connects and/or enters the main event loop.
I have it. Launching isn't too bad, but the menus are horrible. Window switching gets better the longer you run it. There aren't too many new features that I could find. It looks exactly like it would in 9 with a keliedoscope aqua theme on V4. So nice to say bye bye to cliassic