Few issues...
Firstly, it seems odd, but itunes application may not appear on screen when opening, but instead you hear a *beep*.
Although the app is open, you cannot see window (it appears in task switcher and light is lit on dock icon)
To get round this, connect your device first... then itunes always appears on-screen
Makes no sense, but it works...
In addition, when device is connected iTunes does not remember last view (window or full screen)..
Instead, it does still open, but it alternatives first, then after closes, goes to the other one.
Could be a config issue. maybe trash itunes plist files ?
In addition if you have Mission Control set up with the App Store app to open on one specific Desktop, if you have other apps open on a different one, and you attempt to go to "About this Mac" then check for updates button, it shifts desktops two one location, then back to another, instead of just one shift.