After comparing TBC Classic Beta (2.5.1.38644) and the original TBC 2.4.3 (8606) (Jul 10 2008) on a private server, I noticed that things were missing on the current TBC beta :
It was possible to see the numbers of hp and mana and other resources on the target’s portrait (tbc 2.5.1 shows only hp percentage yet)
an interface setting allowed to display the numbers on the experience bar
the world map button was next to the minimap
an interface setting allowed to display the number of free space in the bags
It was possible to see the FPS in the tooltip of the latency bar
Also we can see that the Looking For Group tool is not ready yet.
I think they are using Omar’s some sort of importing software (for the modern client) and then just manually fixing bugs that appear on the side (or as the consequence of import).