I've used both (D7 and BDSD2006+ versions) for multiple years each, and never saw something fundamentally better. Yes. If you are used to one system, it is hard to change.
It is quite obvious where advantages are:
- You don't have to adjust windows size and position with docked id, it simply fills all assigned area. with docking you can very simply divide working area to needed regions
- If you are working with remote desktop from multiple computers (remote desktop or nx desktop) you have to deal with changing desktop size and need to adjust all non docked forms to fit it
- If you use non docked forms you often either saw desktop and other windows in blank space between forms or your undocked forms are lay over others
- Docked system have usually ability to pin/unpin windows in tabs and able to simply and effectively pop out windows temporary. it is handy features mainly on small size monitors.
Then you should simply agree that it is better and only state that nobody have time to implement it so far as usual.
Eclipse, Netbeans, Visual Studio, Monodevelop, Codeblocks, Monkey Studio, Embarcadero RAD Studio, mikroelekronika IDE and many more already proved it is better.
I tried to implement it for myself and found out that there are move obstacles to deal with. To name some: weird forms auto size mechanism which sometimes leads to infinite loop and error message, multiplatform support for vertical tabcontrol (gtk2 not support such), use somehow theme manager for consistent look & feel with multiplatform aspect, and other. Yes, it is bit difficult piece of technology. There are some delphi examples on torry site and also source of JEDI VCL docking implementation to learn on inspire from.