In addition, users upgrading from 10.04 LTS to 12.04 LTS are already getting Unity (which is already in itself a breaking change). I see no reason to delay the introduction of this menu system.
As a user jumping between LTS versions I welcome both the introduction of Unity and the addition of keyboard-driven, menu searches.
I see your point though: maybe a better solution would be to have it in the LTS but disabled by default?
Of course, if it was already installed on the system pre-update it would install and update Unity/HUD.
They could also make it an option on their already very option heavy (which is good) download page.