The Track menu contains commands for creating new tracks, deleting and grouping, along with other track-related functions like Split Mono and Make Inactive.
Similarly, the Region menu contains Region-related commands, and the Event menu is where you'll find most of the commands for manipulating MIDI and Tempo Events that were stored in the MIDI menu in previous versions.
RTAS plug-ins also gain full side-chain capabilities in TDM, and can also be used in the full mono-in/stereo-out configurations.
Pro Tools HD users pay one slight penalty for the more flexible RTAS configuration, though, which is that instead of using a DSP chip to run something like the HTDM Stream Manager, RTAS plug-ins now use the same Voices that audio tracks use to transfer audio to and from the TDM Mixer.
I didn't find this to be as severe as it sounds, though: for example, on my Powerbook I could get 34 four-band Sessions which isn't backwardly compatible with the previous format.