1. Due to the new docking/tabbing of the VE Pro 5 user interface, you can switch between the Mixer and the shared Instrument window like in VE Pro 4 by pressing F3 or F4, which show/hide the Mixer and Instrument window respectively. Those function keys effectively replace the Esc key.
2. How would a user quickly open the channel GUI from the Mixer when it's not possible to doubleclick the label any longer? It would basically trade one function for the other. Since renaming is a far less frequently used function it makes sense to have it in the context menu. Also you can still rename by clicking the name in the Channels window.
3. The transport play/stop transmission will only work if the master host has the space bar set as transport play/stop key. Also currently it doesn't work locally with Pro Tools on OS X as well as Digital Performer. I'm working on getting this fixed as soon as possible however.
Only the first point is a change from VE Pro 4 (just the key changed, not the functionality). The third point is indeed a bug that should be fixed as soon as possible. So I'm not really sure how it is a step backwards :)