There is lots of weird functionality in perspective viewport navigation, and many missing features for it to be usable.

• Navigation controls. ( remove functionality of changing manipulator mode with Ctrl and Alt )
• Navigation controls. ( Create Alt + click based navigation)
• Deselecting object. ( clicking to empty space in view currently does not deselect the selected object. ) in 2.0
• Background gradient. ( Background color should be gradient, to avoid solid color graphics to disappear in viewport ) in 2.0
• Camera object in perspective view ( no way to see what direction camera is looking ) in 2.0
• Light objects in perspective view ( no way to see range of pointlight in viewport etc.. )
• Missing World axis helper, so you will get lost in the viewport ( top right corner of attached image )
• Missing Grid ( No way to visually compare size and distance between objects )
• Camera preview to perspective view ( boolean to control between layer/all layers mode )